Definition of "crawler"

crawler¹

noun
plural crawlers
1. A child who is able to creep using its hands and knees but is not able to walk.
2. (sports) A crawl swimmer.
3. A tractor crawler, a motorized vehicle that uses caterpillar tracks instead of wheels.
4. (Internet) A software bot that autonomously follows connected paths such as links between web pages.
  Quotations
  Crawler-based search engines have three major elements. The first is the spider, also called the crawler, which visits a web page, reads it, and then follows links to other pages within the site.
  2008, Alex Michael, Ben Salter, Marketing Through Search Optimization, Routledge, page xii
  These serve as an algorithmic way to judge the “mobileness” of a site, and similar algorithms are likely to be used by the search crawlers.
  2011, James Pearce, Professional Mobile Web Development with WordPress, Joomla! and Drupal, page 466
5. A mobile stage in the development of stationary hemipteran insects such as scale insects—generally the first instar.

crawler²

noun
plural crawlers
1. (Australia, obsolete) A person who is abused, physically or verbally, and returns to the abuser a supplicant.
2. (UK, Australia, slang) A sycophant.