self-deprecating; self-mocking
Describes a person, remark, or attitude that belittles or makes fun of oneself, often with a humorous or humble tone.
He gave a self-deprecating smile.
He lightened the mood with a self-mocking joke.
Compound of 自嘲 (self-mockery) + 的 (-like, -ish). The exact historical derivation is uncertain, but the word follows a common pattern for forming adjectival nouns.