Definition of catercorner:
(adj) :
of or pertaining to something at a
diagonal to another; of four corners, those diagonal to another
"the Empire State Building and the old Altman's Deparment store are catercorner, at Fifth Avenue and East 34th Street, with the ESB at the southwest, and Altman's at the northeast."
(v) :
diagonally across from
"altman's is sited catercorner to the ESB."