lummoxinformal
lump(PERSON)informal
 SMART Vocabulary: related words and phrases 
 Stupid and silly people 
airhead
berk
birdbrain
blithering idiot
blockhead
dullard
dumb-ass
dummy
dunce
dunderhead
muppet
mutt
need
need your head examinedidiom
nimrod
simpleton
stupid
thicko
tosser
troglodyte
oaf | American Dictionary
oaf
noun[ C ]
us/oʊf/
a big, stupid, awkward person, esp. a man