ludicrous

Concise Oxford English Dictionary © 2008 Oxford University Press:
ludicrous/ˈluːdɪkrəs/

▶adjective so foolish or unreasonable as to be amusing; absurd or ridiculous.

– derivatives
ludicrously adverb,
ludicrousness noun.

– origin C17 (in the sense ‘intended as a jest’): from L. ludicrus (prob. from ludicrum ‘stage play’) + -ous.