1.  mutual(s = adj.all) common - common to or shared by two or more parties; "a common friend"; "the mutual interests of management and labor"
Derived forms noun mutuality₂, noun mutuality₁

2.  mutual(a = adj.all) reciprocal - concerning each of two or more persons or things; especially given or done in return; "reciprocal aid"; "reciprocal trade"; "mutual respect"; "reciprocal privileges at other clubs"
Derived forms noun mutuality₂, noun mutuality₁, noun mutualness₁

1.  Reciprocally acting or related; reciprocally receiving and giving; reciprocally given and received; reciprocal; interchanged; as, a mutual love, advantage, assistance, aversion, etc. [1913 Webster]
"Conspiracy and mutual promise." [1913 Webster]
"Happy in our mutual help,
And mutual love." [1913 Webster]
"A certain shyness on such subjects, which was mutual between the sisters." [1913 Webster]

2.  Possessed, experienced, or done by two or more persons or things at the same time; common; joint; as, mutual happiness; a mutual effort. Burke. [1913 Webster]
"A vast accession of misery and woe from the mutual weeping, and wailing, and gnashing of teeth." [1913 Webster]
"Mutual, as Johnson will tell us, means something reciprocal, a giving and taking. How could people have mutual ancestors?" [1913 Webster]

mutual, adj.
1 (of feelings, actions, etc.) experienced or done by each of two or more parties with reference to the other or others (mutual affection).
2 colloq. disp. common to two or more persons (a mutual friend; a mutual interest).
3 standing in (a specified) relation to each other (mutual well-wishers; mutual beneficiaries).

Idiom:
mutual fund US a unit trust. mutual inductance the property of an electric circuit that causes an electromotive force to be generated in it by change in the current flowing through a magnetically linked circuit. mutual induction the production of an electromotive force between adjacent circuits that are magnetically linked. mutual insurance insurance in which some or all of the profits are divided among the policyholders.

Derivative:
mutuality n. mutually adv.

Etymology:
ME f. OF mutuel f. L mutuus mutual, borrowed, rel. to mutare change

N  correlation, reciprocalness, reciprocity, reciprocation, mutuality, correlation, interdependence, interrelation, connection, link, association, interchange, exchange, barter, reciprocator, reprocitist, reciprocal, mutual, commutual, correlative, reciprocative, interrelated, closely related, alternate, interchangeable, interdependent, international, complemental, complementary, mutually, mutatis mutandis, vice versa, each other, one another, by turns, reciprocally, happy in our mutual help.

N  interchange, exchange, commutation, permutation, intermutation, reciprocation, transposition, rearrangement, shuffling, alternation, reciprocity, castling (at chess), hocus-pocus, interchangeableness, interchangeability, recombination, combination, barter, tit for tat, cross fire, battledore and shuttlecock, quid pro quo, interchanged, reciprocal, mutual, commutative, interchangeable, intercurrent, combinatorial, recombinant, in exchange, vice versa, mutatis mutandis, backwards and forwards, by turns, turn and turn about, each in his turn, everyone in his turn.

coefficient of mutual induction, mutual affection, mutual aid, mutual attraction, mutual company, mutual exclusiveness, mutual fund, mutual inductance, mutual induction, mutual opposition, mutual resemblance, mutual savings bank, mutual understanding