I. ˈ ̷ ̷ ̷ ̷ˌ ̷ ̷ noun
Etymology: under (III) + pass
: a passage beneath:
a. : a grade separation where clearance to traffic on the upper level is obtained by depressing partially or completely (as with a tunnel) the grade of the lower level — compare overpass
b. : the lower level of a grade separation — called also undercrossing
II. transitive verb
: to provide (a crossing) with an underpass