grammaticality - Is "conversate" a word?

Conversate: To converse, to participate in a conversation.

My parents conversate with me over dinner every night.

Is this a word? Spell check says no, but I have heard it used.

Answer

Conversate is a back-formation from conversation, similar to orientate (which is quite common in the UK), administrate, and others.

While some back-formations can even become standard, conversate is decidedly nonstandard. However, it is not surprising that you have heard it used, because it is a word that is employed in some dialects. It is most commonly used in AAVE, a dialect of American English.

Those who use conversate dialectally might be aware of the word converse, but choose not to use it either because conversate carries with it a difference in register/connotation that they want to employ, or because conversate has a slightly different meaning from converse in that dialect.

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These -ate back-formations happen because most nouns ending in -ation have a corresponding verb ending in -ate, but not all of them do. At some point in the past 400 years, the suffix -ment, which used to be a common way of converting verbs to nouns (govern -> government), was overtaken by the more productive -ation. There were so many -ate verbs springing up in English that could all be suffixed with -ion, that this -ation string was reanalyzed in English as a separate suffix (in addition to -ate and -ion) that could be attached to verbs that did not end in -ate. Nowadays, -ment is more or less unused, while -ation continues to be popular. For example, all verbs ending in -ize can be converted to -ization, even though there are no -izate verbs at all; verbs ending in -ify become -ification. And so on.

So, with an -ation word, there are always two possibilities to create a verb: subtract -ion and get an -ate verb, or subtract -ation. Sometimes people create an -ate form spontaneously where none existed, either because of a speech error, a lack of awareness of the original verb, or perhaps because the -ate form sounds better prosodically. There is often a resistance to such a change, and so most of these back-formed -ate words don't extend beyond dialectal use, or don't even take hold at all. But very occasionally, the -ate form can become standard, as orientate arguably has in UK English.

Incidentally, this is how many other types of standard words have come into existence: innovation/error/randomness → dialectal use → standard use.