HWY. SIGN is an abbreviation for highway sign, which is a type of sign used to provide information to drivers on the road. The three crossword solutions for HWY. SIGN are ALT (3 letters), JCT (3 letters), and SLO (3 letters). ALT stands for alternate route, which is a route that can be taken as an alternative to the main route. JCT stands for junction, which is a place where two or more roads meet. SLO stands for slow, which is a warning sign indicating that drivers should reduce their speed.