n. & v.
n. 1 an artificial underground passage through a hill or under a road or river etc., esp. for a railway or road to pass through, or in a mine. 2 an underground passage dug by a burrowing animal. 3 a prolonged period of difficulty or suffering (esp. in metaphors, e.g. the end of the tunnel). 4 a tube containing a propeller shaft etc.
v. (tunnelled, tunnelling; US tunneled, tunneling) 1 intr. (foll. by through, into, etc.) make a tunnel through (a hill etc.). 2 tr. make (one's way) by tunnelling. 3 intr. Physics pass through a potential barrier. tunnel diode Electronics a two-terminal semiconductor diode using tunnelling electrons to perform high-speed switching operations. tunnel-kiln a kiln in which ceramic ware is carried on trucks along a continuously-heated passage. tunnel-net a fishing-net wide at the mouth and narrow at the other end. tunnel vision 1 vision that is defective in not adequately including objects away from the centre of the field of view. 2 colloq. inability to grasp the wider implications of a situation. tunneller n.
[ ME f. OF tonel dimin. of tonne TUN ]