The Collaborative International Dictionary of English v.0.48:

groovy \groov"y\ (gr[=oo]"v[y^]), a.
   Very pleasant or very enjoyable; marvelous; wonderful;
   excellent; -- expressing strong approval, usually of
   enjoyable experiences. [informal, 1960's] [WordNet sense 1]

   Syn: bang-up, bully, cool, corking, cracking, dandy, far-out,
        great, keen, neat, nifty, not bad(predicate),
        out-of-sight, outtasight, peachy, psychedelic, slap-up,
        swell, smashing.
        [WordNet 1.5 +PJC]

   2. Very chic; as, groovy clothes. [British informal] [WordNet
      sense 2]

   Syn: swagger.
        [WordNet 1.5]

   3. same as hip. [informal, 1960's]

   Syn: hip, with it.
        [PJC]

WordNet (r) 3.0 (2006):

groovy
    adj 1: very good; "he did a bully job"; "a neat sports car";
           "had a great time at the party"; "you look simply
           smashing" [syn: bang-up, bully, corking,
           cracking, dandy, great, groovy, keen, neat,
           nifty, not bad(p), peachy, slap-up, swell,
           smashing]
    2: (British informal) very chic; "groovy clothes" [syn:
       groovy, swagger]

Moby Thesaurus II by Grady Ward, 1.0:

56 Moby Thesaurus words for "groovy":
   OK, ace-high, bad, bang-up, bonzer, boss, bully, but good, cool,
   corking, crackerjack, dandy, delicious, divine, ducky, fab,
   fine and dandy, gear, glorious, go-go, goody, great, heavy, hep,
   hip, hot, hunky-dory, into, jam-up, just dandy, keen, marvy, mean,
   neat, nifty, nobby, okay, on the beam, out of sight, peachy,
   peachy-keen, really into, ripping, rum, scrumptious, slap-up,
   smashing, solid, something else, spiffing, spiffy, stunning, swell,
   tough, with it, wizard