Learner's definition of TENUOUS
[more tenuous; most tenuous]
not certain, definite, or strong
flimsy, weak, or uncertain
He has a tenuous grasp/grip/hold on reality.
a tenuous hypothesis/relationship
The local theater has had a tenuous existence in recent years.
He could demonstrate only a tenuous claim to ownership.
The connection between his absence and the robbery is tenuous [=shaky] at best.