(1):

(v. t.) To perform by turns, or in succession; to cause to succeed by turns; to interchange regularly.

(2):

(n.) A proportion derived from another proportion by interchanging the means.

(3):

(a.) Being or succeeding by turns; one following the other in succession of time or place; by turns first one and then the other; hence, reciprocal.

(4):

(a.) Designating the members in a series, which regularly intervene between the members of another series, as the odd or even numbers of the numerals; every other; every second; as, the alternate members 1, 3, 5, 7, etc.; read every alternate line.

(5):

(a.) Distributed, as leaves, singly at different heights of the stem, and at equal intervals as respects angular divergence.

(6):

(n.) That which alternates with something else; vicissitude.

(7):

(n.) A substitute; one designated to take the place of another, if necessary, in performing some duty.

(8):

(v. i.) To vary by turns; as, the land alternates between rocky hills and sandy plains.

(9):

(v. i.) To happen, succeed, or act by turns; to follow reciprocally in place or time; - followed by with; as, the flood and ebb tides alternate with each other.