A2[IorT]totouchwithyourlips,especiallyas agreeting, or topressyourmouthonto another person'smouthin asexualway:
There was ayoungcoupleon thesofa, kissingpassionately.
She kissed himonthemouth.
[+ two objects]He kissed thechildrengoodnight/goodbye(= kissed them as apartof saying goodnight/goodbye).