phrase: get off it

The text seems inaccurate on the page:
reference (slash) phrasal-verbs (slash) get+off+it (dot) html

It says "get off it" is a way of expressing disbelief. Though this would be true in a situation in which the phrase is used, there's more to the meaning.

In the extensive usage of this that I've heard, "get off it" is a command telling someone to relinquish their position/opinion on an issue. Like if I yell at you, "You did that on purpose!" The person might say, "No way- get off it!" It's particularly used about very subjective opinions that where the position makes one right or makes others wrong.

In the 1970's, it was used extensively by the Erhard Seminars Training organization and is still used by its successor, Landmark Education. It's a phrase commonly used in their courses which have been delivered to about 2 million people. It's also used in phrases, "being on it" ("I'm on it about money being scarce") and "getting off it" ("I'm getting off it about my wife's yelling meaning she's angry at me- to her, she's just expressing frustration.")

A similar expressing is "get over it", commanding someone to "let go" of the emotional significance fueling the certainty and significance with which they are holding the opinion.

(I don't know if the term originated with est, but it seems likely, and especially likely that they brought it into the culture.)

Thanks for that- I will extend the definition.

Is 'get off' used in this sense anywhere outside the organisations mentioned? I have looked in quite a few phrasal verb lists online, and can't find it.

The first definition was submitted by an American speaker to me who did know their onions. It's hard to know where to draw lines, but if something has been used this much, then inclusion in an online list seems OK to me. There are verbs in there that I have come across that aren't in things like the Cambridge dictionary of PVs. I can always remove it if it is wrong. Room in, for example, is used in medical contexts, but few dictionaries have picked up on it.

We do get a fair number of dishonest idioms- for some reason people want to get definitions of idioms into dictionaries and we have had a lot of false ones, but not phrasal verbs. (yet)

I think that it is sometimes used as a sort of short-hand to "get off your high horse", and that is where the additional meaning may come from, i.e. a retort to make the other person relinquish their position.