Nonexistent means not existing at all. Virtually nonexistent, a nonexistent problem, nonexistent evidence.
It is usually an exaggeration for something very scarce rather than a claim that there is none, and virtually nonexistent is the standard hedge for exactly that. It is written as one word in America and often hyphenated in Britain.
1adjectivenonexistentNot existing at all.
“Public transport in the village is almost nonexistent; there's one bus a week.”
nonexistent is a state.
Non- plus existent, from Latin existere, to come forth or stand out.
From non- + existent.
Etymology from Wiktionary, CC BY-SA