That moves backwards and forwards.

present participle of reciprocate

Third-person singular simple present indicative form of reciprocate

simple past tense and past participle of reciprocate

In a reciprocal manner; by way of returning (e.g. a favour, insult, etc).

(arithmetic) The number obtained by dividing 1 by another given number; the result of exchanging the numerator and the denominator of a fraction. / (grammar) A construction expressing mutual action.

Of a feeling, action or such: mutual, uniformly felt or done by each party towards the other or others; two-way. / Mutually interchangeable.

The characteristic of being reciprocal, e.g. of a relationship between people. / A reciprocal relationship. / A relation of mutual dependence or action or influence.

(transitive) To exchange two things, with both parties giving one thing and taking another thing.

The act of reciprocating; interchange of acts; a mutual giving and returning / Alternate recurrence or action; as, the reciprocation of the sea in the flow and ebb of tides; oscillation.