suru verb (irregular), intransitive verb
Intransitive verb meaning to expel saliva from the mouth. Often used in the set phrase 天に唾する (to spit at heaven; to harm oneself by trying to harm someone else).
See also: 天に唾する
道に唾するのはやめなさい。
Stop spitting on the road.
天に唾するようなこと
Don't do something like spitting at heaven (i.e., don't harm yourself by trying to harm others).