n.
1.a passageway through or under something, usually underground (especially one for trains or cars)
2.a hole in the ground made by an animal for shelter tunnel v.
1.move through by or as by digging
2.force a way through
Idiom of the Day
put (something) on the line
to speak very firmly and directly about something
I put my reputation on the line when I supported my friend and his business proposal.