'Old Nick' definitions:

Definition of 'Old Nick'

(from WordNet)
noun
(Judeo-Christian and Islamic religions) chief spirit of evil and adversary of God; tempter of mankind; master of Hell [syn: Satan, Old Nick, Devil, Lucifer, Beelzebub, the Tempter, Prince of Darkness]

Definition of 'Old Nick'

From: GCIDE
  • Nick \Nick\ (n[i^]k), n. [AS. nicor a marine monster; akin to D. nikker a water spite, Icel. nykr, ONG. nihhus a crocodile, G. nix a water sprite; cf. Gr. ni`ptein to wash, Skr. nij. Cf. Nix.] (Northern Myth.) An evil spirit of the waters. [1913 Webster]
  • Old Nick, the evil one; the devil. [Colloq.] [1913 Webster]