noun

• (uncountable) Milk drawn from the breast.
  "The infant took suck in an instant, pulling strongly."
• (uncountable) The ability to suck; suction.
  "Vacuum for the park Mosuc is a street and park vacuum cleaner which its designers, Hollowell Engineering, Dearborn, Michigan, like to claim has more suck than most[.]"
• (Canada) A weak, self-pitying person; a person who refuses to go along with others, especially out of spite; a crybaby or sore loser.
  "“Why're you bothering to take her anywhere? I can't stand traveling with her. You're such a suck,” her sister said. Waved her smoke. “No fucking way I'm going.”"
• (slang, dated) A short drink, especially a dram of spirits.

verb

• (transitive) To use the mouth and lips to pull in (a liquid, especially milk from the breast).
  "The baby sucked (milk) on her bottle."
• (intransitive) To perform such an action; to feed from a breast or teat.
• (transitive) To put the mouth or lips to (a breast, a mother etc.) to draw in milk.
• (transitive) To extract, draw in (a substance) from or out of something.
  "That she may sucke their life, and drinke their blood, / With which she from her childhood had bene fed."