head off

verb

1. to intercept and force to change direction

   to head off the stampede

2. to prevent or forestall (something that is likely to happen)

3. to depart or set out

   to head off to school

Idioms and Phrases

Block the progress or completion of; also, intercept. For example, They worked round the clock to head off the flu epidemic, or Try to head him off before he gets home. [First half of 1800s] This expression gave rise to head someone off at the pass, which in Western films meant “to block someone at a mountain pass.” It then became a general colloquialism for intercepting someone, as in Jim is going to the boss's office—let's head him off at the pass.