The Collaborative International Dictionary of English v.0.48:

Lobby \Lob"by\, v. i. [imp. & p. p. Lobbied; p. pr. & vb. n.
   Lobbying.]
   To address or solicit members of a legislative body in the
   lobby or elsewhere, with the purpose to influence their
   votes; in an extended sense, to try to influence
   decision-makers in any circumstance. [U.S.] --Bartlett.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "lobbying":
   Byzantine intrigues, allurement, backscratching,
   backstairs influence, blandishment, cajolement, cajolery, coaxing,
   connections, conning, deals, engagement, enlistment, exhortation,
   games, hortation, inducement, influence peddling, intrigues,
   jawboning, lobbyism, logrolling, persuasion, ploys,
   political influence, preaching, preachment, public opinion, ropes,
   sales talk, salesmanship, schemes, selling, snow job,
   social pressure, soft soap, solicitation,
   special-interest pressure, strings, suasion, sweet talk, wheedling,
   wire-pulling, wires, working on