The Collaborative International Dictionary of English v.0.48:

Nip \Nip\, n.
   1. A seizing or closing in upon; a pinching; as, in the
      northern seas, the nip of masses of ice.
      [1913 Webster]

   2. A pinch with the nails or teeth.
      [1913 Webster]

   3. A small cut, or a cutting off the end.
      [1913 Webster]

   4. A blast; a killing of the ends of plants by frost.
      [1913 Webster]

   5. A biting sarcasm; a taunt. --Latimer.
      [1913 Webster]

   6. (Naut.) A short turn in a rope.
      [1913 Webster]

   Nip and tuck, a phrase signifying equality in a contest;
      as, it was nip and tuck right to the last minute of play.
      [Low, U.S.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

nip and tuck
    adv 1: even or close in a race or competition or comparison;
           "the horses ran neck and neck"; "he won nip and tuck"
           [syn: neck and neck, head-to-head, nip and tuck]
    adj 1: inconclusive as to outcome; close or just even in a race
           or comparison or competition; "as they approached the
           finish line they were neck and neck"; "the election was a
           nip and tuck affair" [syn: neck and neck, head-to-
           head, nip and tuck]
    n 1: plastic surgery to remove wrinkles and other signs of aging
         from your face; an incision is made near the hair line and
         skin is pulled back and excess tissue is excised; "some
         actresses have more than one face lift" [syn: face lift,
         facelift, lift, face lifting, cosmetic surgery,
         rhytidectomy, rhytidoplasty, nip and tuck]

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "nip and tuck":
   alike, at par, au pair, commensurate, drawn, equal, equalized,
   even, even stephen, fifty-fifty, half-and-half, knotted, level,
   like, on a footing, on a level, on a par, on even ground, par,
   proportionate, quits, square, stalemated, tied