What does "companion" mean?

Additional senses

1. 2.A fellow; -- in contempt. [Obs.] Shak.
2. 3.Etym: [Cf. OSp. compaña an outhouse, office.] (Naut.) (a) A skylight on an upper deck with frames and sashes of various shapes, to admit light to a cabin or lower deck. (b) A wooden hood or penthouse covering the companion way; a companion hatch. Companion hatch (Naut.), a wooden porch over the entrance or staircase of the cabin. -- Companion ladder (Naut.), the ladder by which officers ascend to, or descend from, the quarter-deck. Totten. -- Companion way (Naut.), a staircase leading to the cabin. -- Knights companions, in certain honorary orders, the members of the lowest grades as distinguished from knights commanders, knights grand cross, and the like.
3. 4.To be a companion to; to attend on; to accompany. [R.] Ruskin.
4. 5.To qualify as a companion; to make equal. [Obs.] Companion me with my mistress. Shak.