noun

1. Obsolete
   1. a flue
   2. a funnel
2. a passageway, as through a mountain or under a body of water, as for automotive or rail traffic
3. an animal's burrow
4. any tunnel-like passage, as one in a mine

Etymology: ME tonel, a net with wide opening and narrow end < MFr tonnelle, arbor, semicircular vault < OFr tonnel, dim. of tonne, tun

transitive verb tunneled -·neled or tunnelled -·nelled, tunneling -·nel·ing or tunnelling -·nel·ling

1. to dig (a passage) in the form of a tunnel
2. to make a tunnel through or under
3. to make (one's way) by digging a tunnel

intransitive verb

1. to make a tunnel
2. Physics to pass through a normally impassable barrier or insulator electrons tunnel through semiconductors