Wiktionary
n. A bicycle or motorcycle which is designed and used for off-road travel on rugged or inclined surfaces.
WordNet
Usage examples of "trail bike".
So I cranked up my trail bike and drove up to where I could stake out the cave.
On a wild hunch he jumped on his trail bike and explored the dirt roads surrounding Mooseville, where Iggy might park his truck and pass out for a couple of days.
It is not a creature at all, but a machine, and it is called a trail bike.
We were on a screaming red and yellow Honda trail bike with me perched uneasily behind him.
This wasn't an off-trail bike, and in any event, this terrain wasn't for any wheeled vehicle.
That's when he nodded and said thanks and riffled the stack with his thumb and shoved it into the saddlebag on the trail bike.
On the way back a fat man on a rackety little trail bike nearly ran me down, then yelled out his estimate of my ancestry and lineage.