The Collaborative International Dictionary of English v.0.48:

Hobnob \Hob"nob`\, n.
   Familiar, social intercourse. --W. Black.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Hobnob \Hob"nob`\, adv. [AS. habban to have + habban to have
   not; ne not + habban to have. See Have, and cf. Habnab.]
   1. Have or have not; -- a familiar invitation to reciprocal
      drinking. --Shak.
      [1913 Webster]

   2. At random; hit or miss. (Obs.) --Holinshed.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Hobnob \Hob"nob`\, v. i. [imp. & p. p. Hornobbed; p. pr. & vb.
   n. Hornobbing.]
   1. To drink familiarly (with another). [ Written also
      hob-a-nob.]
      [1913 Webster]

   2. To associate familiarly; to be on intimate terms; as, to
      hobnob with the political elite.
      [1913 Webster]

WordNet (r) 3.0 (2006):

hobnob
    v 1: rub elbows with; "He hobnobs with the best of society"