隔壁老王

gé bì lǎo wáng

Mr Wang from next door (term used jocularly to refer to a neighbor who is supposedly sleeping with one's wife)

隔

gé

to separate

壁

bì

wall

老

lǎo

prefix used before the surname of a person or a numeral indicating the order of birth of the children in a family or to indicate affection or familiarity

王

wáng

king or monarch