Gila monster UK /ˈhiːlə ˈmɒnstə(ɹ)/US /ˈhilə ˈmɑnstɚ/ noun1 •A venomous lizard, Heloderma suspectum, that lives in the deserts of the southwestern USA and northwestern Mexico.Ever see one a them Gila monsters take hold, mister? Grabs hold, an’ you chop him in two an’ his head hangs on. — 1939 formsGila monsters