What does "mate" mean?

Additional senses

1. 2.To checkmate.
2. 3.One who customarily associates with another; a companion; an associate; any object which is associated or combined with a similar object.
3. 4.Hence, specifically, a husband or wife; and among the lower animals, one of a pair associated for propagation and the care of their young.
4. 5.A suitable companion; a match; an equal. Ye knew me once no mate For you; there sitting where you durst not soar. Milton.
5. 6.(Naut.) An officer in a merchant vessel ranking next below the captain. If there are more than one bearing the title, they are called, respectively, first mate, second mate, third mate, etc. In the navy, a subordinate officer or assistant; as, master's mate; surgeon's mate.
6. 7.To match; to marry. If she be mated with an equal husband. Shak.
7. 8.To match one's self against; to oppose as equal; to compete with. There is no passion in the mind of man so weak but it mates and masters the fear of death. Bacon. I, . . . in the way of loyalty and truth, . . . Dare mate a sounder man than Surrey can be. Shak.
8. 9.To be or become a mate or mates, especially in sexual companionship; as, some birds mate for life; this bird will not mate with that one.