Definition of timberline in US English:

timberline

noun

North American
  • 1(on a mountain) the line or altitude above which no trees grow.

    Also called tree line
    1. 1.1 (in high northern (or southern) latitudes) the line north (or south) of which no trees grow.

Pronunciation

timberline

/ˈtimbərˌlīn//ˈtɪmbərˌlaɪn/