Definition of off-trail in US English:

off-trail

adverb

  • Off a trail or path; away from an established route.

adjective

  • That is or takes place away from a trail; specifically (of a sport, activity, etc.) conducted away from an established or conventional route. Also (and in earliest use) figurative: different to that which is accepted or usual; unorthodox.

Origin

Late 19th century; earliest use found in Overland Monthly. From off + trail.