In chat, there are some commands such as "translate" and "wiki". The "translate" command accepts any language and translates that text to English (the Stack Exchange/Feeds user replies with the English text), and "wiki: yourtexthere" transforms your message into a Wikipedia onebox to the article you referred (see this and this message).
Is there a full list of these commands available?
The "translate" command started as something nice to have, probably on a whim by Marc (i.e. not an official feature), and was removed after being abused by many users.
Marc tried to fight it, e.g. in The automated Stack Exchange / Feeds user is now participating in chat but eventually gave up four days later and nuked this featue with a blast of "This is why we can't have nice things" all over chat:
Yes, yes; I was turning off the much-abused translate bot; I intended for subsequent use of translate: foo to result in that message, but... an if block got in the wrong place. Bad things. Very bad things. Fixed; data cleansed (but still tidying up a bit...)
I am pretty sure this abuse also prevented any further features, and we won't ever see anything like that again, as people will always abuse it.
Neither of the commands you mention are still active.
The "translate: text to translate" was moderator only most recently but it stopped working in May of 2017.
They've also added automatic oneboxing for links from a few sites, so you don't need a command for them.
This includes:
define: and wiki: seem to work (for non-mods too) at the moment.