to act or interpose in behalf of someone in difficulty or trouble, as by pleading or petition

to intercede with the governor for a condemned man.

to attempt to reconcile differences between two people or groups; mediate.

Roman History . (of a tribune or other magistrate) to interpose a veto.

verb

advocate , arbitrate , barge in , butt in * , intermediate , interpose , intervene , intrude , mix in , monkey with , negotiate , plead , reconcile , speak , step in , mediate , propitiate