Noah Webster's New International Dictionary of the English Language

1. (a.) Reciprocally acting or related; reciprocally receiving and giving; reciprocally given and received; reciprocal; interchanged; as, a mutual love, advantage, assistance, aversion, etc.

2. (a.) Possessed, experienced, or done by two or more persons or things at the same time; common; joint; as, mutual happiness; a mutual effort.