reciprocate

verb

• 1 [with object] respond to (a gesture or action) by making a corresponding one:the favour was reciprocated [no object]:perhaps I was expected to reciprocate with some remark of my own
• feel (affection or love) for someone in the same way that they feel it for oneself:her passion for him was not reciprocated

• 2 [no object] (usually as adjective reciprocating) (of a part of a machine) move backwards and forwards in a straight line:a reciprocating blade