Lechy
From what I know, "lechy" is used in spoken British English to mean "lecherous", i.e. exceedingly interested in sex, and in an obsessive and unpleasant way. Usually, it is associated with men, more particularly middle-aged and older, who lust after younger women.
Look at that lechy man over there! Have you noticed the way he is staring at the boobs of the waitress, who would be young enough to be his daughter!