Green’s Dictionary of Slang

dipsy n.2

[? dipso n. / dipstick n. (2)]

(US) a mentally retarded person.

[US]R. Campbell Sweet La-La Land (1999) 153: Is this the sonofabitch? Is the dipsy right? Is this the cocksucker what done your friend?
[US]T. Dorsey Hurricane Punch 10: He was Dipsy the Hippie Cop.