What is the meaning of pitting?

noun

• The formation of small pits in a surface as a consequence of corrosion.
  • synonyms: roughness, indentation

verb

• Set into opposition or rivalry.
  • usage: "let them match their best athletes against ours"; "pit a chess player against the Russian champion"; "He plays his two children off against each other"
  • synonyms: pit, oppose, match, play off
• Mark with a scar.
  • usage: "The skin disease scarred his face permanently"
  • synonyms: scar, mark, pock, pit
• Remove the pits from.
  • usage: "pit plums and cherries"
  • synonyms: pit, stone