In Mayan culture, colours seem to have been used as names for the primary directions: for instance, "red" implies east as the colour of sunrise. So the following might be a stylish touch for a game in which the player has to get inside the Mayan world-view:

"Indirection"

Understand "white" and "sac" as north. Understand "red" and "chac" as east. Understand "yellow" and "kan" as south. Understand "black" and "chikin" as west.

We could also use a colour as a verb:

Understand "turquoise" and "yax" as looking.

And now a few extra rooms to try it out in:

The Square Chamber is a room. "A sunken, gloomy stone chamber, ten yards across. A shaft of sunlight cuts in from the steps above, giving the chamber a diffuse light, but in the shadows low lintelled doorways to east and south lead into the deeper darkness of the Temple."

The Wormcast is east of the Square Chamber. The Corridor is south of the Square Chamber.

Test me with "kan / white / chac / black".

We have seen before how to define a new action from scratch, but we may want to review here, using a simple command that requires no objects.

"XYZZY"

Understand "xyzzy" or "say xyzzy" or "cast xyzzy" as casting xyzzy.

Casting xyzzy is an action applying to nothing.

Check casting xyzzy:
    if the player does not wear the amulet of elocution, say "You are unable to articulate the second 'z' separately from the first, and the spell fails in a disdainful puff. Must be Parisian magic." instead;
    if the player has the plate, say "The plate of cheeses twitches uncomfortably, aware that it should be doing something, but not sure what." instead.

Carry out casting xyzzy:
    move the plate to the player.

Report casting xyzzy:
    say "Under the influence of the Amulet of Elocution, you pronounce this as Xhi-zee. And lo, from nowhere, a [plate] appears!"

The amulet of elocution is a wearable thing. It is carried by the player. The description is "A heavy gold ring on a chain. If heated in an ordinary house fire, it glows with the words, 'Moses Supposes His Toeses Are Roses.'"

The plate is a portable supporter. On the plate is a very ripe ooze. Instead of smelling the ooze, say "It smells like socks. This is going to be wonderful." The ooze is edible. The printed name of the plate is "plate[if the plate supports the ooze] of cheese[end if]". The description of the ooze is "Definitely genuinely cheese." Understand "cheese" as the ooze.

Instead of eating the ooze: now the ooze is nowhere; say "You are transported..."; move the player to Paradise.

The Cheez Factory is a room. "All around you are squares of pressed orange polymer, or possibly cheez. Your only hope is the magic word your uncle taught you: XYZZY." The squares of pressed orange polymer are scenery in the Factory. The description is "You see nothing special about the squares of pressed orange polymer. Nothing special at all." Understand "square" or "cheez" as the squares.

Paradise is a room. The description is "Well, it might just be one of the posh upper rings of purgatory, if you're entirely honest with yourself."

Test me with "x squares / x amulet / x cheese / xyzzy / wear amulet / xyzzy / x ooze / smell ooze / eat ooze".

XYZZY is a magic word from the original Adventure, and many other games respond to it with some sort of amusing message.

If we wanted to define a brand new verb that did affect a specific object, we might begin like this:

"Xylan"

Understand "hydrolyze [something]" as hydrolyzing. Hydrolyzing is an action applying to one thing.

Carry out hydrolyzing:
    say "[The noun] cannot be hydrolyzed."

Instead of hydrolyzing the xylan:
    move the xylose to the holder of the xylan;
    now the xylan is nowhere;
    say "At once the xylan becomes xylose."

Plant Cell Wall is a room.

There is a xylose sample. The xylan sample is a thing in Plant Cell Wall. The description of the xylan is "A polysaccharide. Totally useless. If only you had some xylose, instead!" The description of the xylose is "Awesome!"

Test me with "x xylan / hydrolyze xylan / x xylose".

Of course, how our players will ever solve this problem is another question (especially if their biology and chemistry are both rusty). When adding entirely new commands to a game, it is often a good idea to provide as many ways of phrasing the command as possible; to drop hints about the correct phrasing within the game's text; or even to tell the player about the expanded command list in some documentation or help at the beginning of the game. So for instance we might also add

Understand "break down [something] with water" or "break [something] down with water" as hydrolyzing.

And these lines will also provide syntax for our new command, without interfering with the previous syntax. It's also good to anticipate alternative (British or American) spellings. People's typing habits are hard to overcome, even if they know you are spelling the word the other way. It is probably best not to annoy them unduly. So:

Understand "hydrolyse [something]" as hydrolyzing.

Then some text in-game might offer a clue, subtle or (since this is an example) blunt:

Instead of examining the player, say "You're a drop of water, which means that you can break down certain chemicals!"

Understand "break down [something]" or "break [something] down" as hydrolyzing.

And finally, we could try adding instructions explicitly:

Understand "help" or "hint" or "hints" or "instructions" or "info" or "about" as asking for help. Asking for help is an action out of world. Carry out asking for help: say "The following commands are understood, in addition to the standard ones: EVAPORATE, FREEZE, HYDROLYZE, SUBLIME..."

Test more with "help / x me / break down xylan"

...though of course in fact these other commands won't be available until we define them, too.

This last approach, defining all the extra commands up front, is especially useful if these commands are very technical or unusual; if they are needed early in the game, before you've a chance to educate the player; or if they are not suggested by any in-game objects. A player who encounters a tool with an obvious use, such as a hairbrush, will likely think of trying to BRUSH things with it. It's harder to rely on his guessing actions that are both outside the range of usual commands and unrelated to any of the visible props, however.