1. n. A vertical tube or hollow column used to emit environmentally polluting gaseous and solid matter (including but not limited to by-products of burning carbon or hydrocarbon based fuels); a flue.
2. n. The glass flue surrounding the flame of an oil lamp.
3. n. (British) The smokestack of a steam locomotive.
4. n. A narrow cleft in a rock face; a narrow vertical cave passage.
5. v. (climbing) To negotiate a chimney (narrow vertical cave passage) by pushing against the sides with back, feet, hands, etc.