a jackass; a dumbass; a moron; an imbecile

April Fools' Day

Alternative spelling of 馬鹿野郎 (“stupid man; prick; dick”)

Someone who has poor handwriting, especially poor knowledge of writing kanji characters, due to habitual use of Japanese computer text input methods rather than pen and paper.

having a comeback or excuse for everything one is told, being smart in the sense of having a smart mouth

(idiomatic) just as [someone] says

as a matter of fact; to tell the truth

saying as much as one wants (usually complaints)

(idiomatic) needless to say, goes without saying

(idiomatic) silence is golden, better left unsaid