промолча́ть

verbperfective (partner молча́ть)fairly commonC2

1.
to remain silent, to say nothing, to keep quiet (instead of answering)
Я спроси́л его, но он промолча́л.
I asked him, but he said nothing.
Perfective; typically of not replying at a particular moment.
2.
to remain quiet for a while
Она́ промолча́ла весь ве́чер.
She stayed silent the whole evening.
With a time expression: silence lasting a certain period.

Examples

Он ехидно улыбнулся и промолчал.
He smiled maliciously and said nothing.
Она слукавила и промолчала о деньгах.
She was evasive and said nothing about the money.
Он хмуро посмотрел на меня и промолчал.
He gave me a sullen look and said nothing.
От боли он покривился, но промолчал.
He winced from the pain but said nothing.
Старик таинственно улыбнулся и промолчал.
The old man smiled mysteriously and said nothing.
Иногда лу́чше промолча́ть.
Sometimes it's better to remain silent.
Она лукаво улыбнулась и промолчала.
She smiled slyly and said nothing.
Лу́чше промолчи́! Зна́ешь, сколько стоит одно сло́во?
You'd better say nothing! Do you know how much a single word is worth?
Он насупил брови и промолчал.
He furrowed his brows and said nothing.
Он недовольно скосился на меня и промолчал.
He glanced at me disapprovingly and said nothing.

Imperative
ты	промолчи́
вы	промолчи́те

Active present	-
Active past	промолча́вший	who kept silent, who remained silent, having kept silent
Passive present	-
Passive past	-
Gerund present	-
Gerund past	промолча́в промолчавши	while doing (past)