The Collaborative International Dictionary of English v.0.48:

Protuberant \Pro*tu"ber*ant\, a. [L. protuberans, -antis, p. pr.
   of protuberare. See Protuberate.]
   Prominent, or excessively prominent; bulging beyond the
   surrounding or adjacent surface; swelling; as, a protuberant
   joint; a protuberant eye. -- Pro*tu"ber*ant*ly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

protuberant
    adj 1: curving outward [syn: bellied, bellying, bulbous,
           bulging, bulgy, protuberant]