interjection
Very casual, masculine-leaning farewell. Often used among close friends or in rough speech; can sound abrupt or dismissive in polite contexts.
「あばよ、また明日な。」
"See ya, see you tomorrow."
彼は手を振って「あばよ」と言った。
He waved and said, "Later."
The exact origin is uncertain. It may be a contraction of a phrase like あば、行くよ or a sound change from an older farewell expression.