Be Sick Meaning

(informal) to vomit

Example: Used other than as an idiom: be sick.
  I am sick today, so can't come to work.
  The dog's been sick all over the carpet.
2011 December 14, Steven Morris, “Devon woman jailed for 168 days for killing kitten in microwave”[1], Guardian:
  The court was told Robins had asked if she could use the oven to heat some baby food for her child. Knutton heard a loud popping noise "like a crisp packet being popped" coming from the kitchen followed by a "screeching" noise. When she saw what had happened to the kitten she was sick in the sink.