Meaning

• A fellow, comrade, colleague, partner or someone with whom something is shared, e.g. shipmate, classmate.

• (especially of a non-human animal) A breeding partner.

• A friend, usually of the same sex.

  "He's my best mate."

• Friendly term of address to a stranger, usually male, of similar age

  "Excuse me, mate, have you got the time?"

• In naval ranks, a non-commissioned officer or his subordinate (e.g. Boatswain's Mate, Gunner's Mate, Sailmaker's Mate, etc).

• A ship's officer, subordinate to the master on a commercial ship.

• A first mate.

• A technical assistant in certain trades (e.g. gasfitter's mate, plumber's mate); sometimes an apprentice.

• The other member of a matched pair of objects.

  "I found one of the socks I wanted to wear, but I couldn't find its mate."

• A suitable companion; a match; an equal.

Meaning

• To match, fit together without space between.

  "The pieces of the puzzle mate perfectly."

• To copulate.

• To pair in order to raise offspring

• To arrange in matched pairs.

• To introduce (animals) together for the purpose of breeding.

• (of an animal) To copulate with.

• To marry; to match (a person).

• To match oneself against; to oppose as equal; to compete with.

• To fit (objects) together without space between.

• To move (a space shuttle orbiter) onto the back of an aircraft that can carry it.