One who promotes the sport of cock-fighting; = COCKER sb.2 2.

1

1721.  Bailey, s.v. Clear Walk, With Cock-fighters.

2

1789.  Cowper (title), The Cock-fighter’s Garland.

3

1884.  T. Holmes Gore, in Law Times, 8 Nov., 28/2. The licensing justices … refused to renew a licence to a cockfighter.

4

  ¶ Co·ck fi·ghter = chief or champion fighter: see COCK sb.1 22.

5