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"informal" is also used as a crossword clue. If that's what you saw, the answer is often colloquial (10 letters).
Definitions
Casual rather than official or formal.
Word origin
From in- + formal.
Used in a sentence
“an informal get-together”
“Students and faculty members lunch at the cafeteria and naturally communicate freely with one another in a relaxed and informal setting.”
“an informal agreement”
Source: Wiktionary, CC BY-SA 4.0
Used as a crossword answer1 curated clues
01“Casual”8 letters
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