The Collaborative International Dictionary of English v.0.48:

blowjob \blow"job`\, blow job \blow" job`\n.
   An act of fellatio, a form of oral sex; -- a slang term.
   See blow[11], v. i. [Vulgar slang]

   Syn: cock sucking.
        [WordNet 1.5 +PJC]

The Collaborative International Dictionary of English v.0.48:

fellatio \fel*la"ti*o\ (f[e^]l*l[=a]"sh[=e]*[-o];
   f[e^]l*l[=a]"t[=e]*[-o]), n.
   a form of sexual activity between two persons in which the
   penis of one is stimulated by the other's mouth, especially
   until orgasm is achieved. It is a form of oral sex. Compare
   cunnilingus. The act is also called by the slang term blow
   job.
   [PJC]