croque-mon·sieur or croque mon·sieur 
(krōk′mə-syœ)
(krōk′mə-syœ)n.
A buttery sandwich of ham, cheese, and sometimes béchamel sauce, that is often dipped in egg before it is grilled.
[French : croquer, to crunch, bite (from Old French *to strike, break, of imitative origin) + monsieur, mister; see MONSIEUR.]