Source : Webster's Revised Unabridged Dictionary (1913)

Crawler \Crawl"er\ (kr?l"?r), n.
   One who, or that which, crawls; a creeper; a reptile.

Source : WordNet®

crawler
     n 1: a person who tries to please someone in order to gain a
          personal advantage [syn: {sycophant}, {toady}, {lackey}]
     2: a person who crawls or creeps along the ground [syn: {creeper}]
     3: terrestrial worm that burrows into and helps aerate soil;
        often surfaces when the ground is cool or wet; used as
        bait by anglers [syn: {earthworm}, {angleworm}, {fishworm},
         {fishing worm}, {wiggler}, {nightwalker}, {nightcrawler},
         {dew worm}, {red worm}]

Source : Free On-Line Dictionary of Computing

crawler
     
        {robot}