stumble over (words)

Translations
запинаться на (словах)
He often stumbles over his words when he's nervous.
Он часто запинается на словах, когда нервничает.
Definitions
To have difficulty speaking clearly or fluently, often resulting in hesitations, mispronunciations, or interruptions.
Words
stumble

verb
запинаться
over

preposition
на
words

noun
словах