If you describe something such as a connection, a reason, or someone's position as tenuous, you mean that it is very uncertain or weak.

What does tenuous mean in a relationship?

From Longman Dictionary of Contemporary Englishten‧u‧ous /ˈtenjuəs/ adjective 1 a situation or relationship that is tenuous is uncertain, weak, or likely to change For now, the band's travel plans are tenuous.

What does it mean when someone is tenuous?

1a : having little substance or strength : flimsy, weak tenuous influences. b : shaky sense 2a tenuous reasons.