seriously doubt

Translations
серьезно сомневаться
I seriously doubt he will come.
Я серьезно сомневаюсь, что он придет.
Definitions
To have a strong skepticism or lack of belief regarding something, indicating that one is not convinced or is highly uncertain about its truth or validity.
Words
doubt

verb
сомневаться
seriously

adverb
серьёзно