sit out transitive verb 1.: to remain to the end of < sit out a dull speech > 2.: to outstay in a social call < determined to sit his rival out > 3. a.: to remain seated during (a dance) b.: to fail to take part in : stay aloof from < believe we would find it impossible to sit out any war in Europe — Elmo Roper > 4.: to stretch the back of (a skirt) by wearing while sitting