What is the meaning of assimilate?

verb

• Take up mentally.
  • usage: "he absorbed the knowledge or beliefs of his tribe"
  • synonyms: absorb, ingest, take in
• Become similar to one's environment.
  • usage: "Immigrants often want to assimilate quickly"
• Make similar.
  • usage: "This country assimilates immigrants very quickly"
• Take (gas, light or heat) into a solution.
  • synonyms: imbibe
• Become similar in sound.
  • usage: "The nasal assimilates to the following consonant"