Like a valid defense

• Not easily debunked
• Not bad, as an argument
• Seemingly rational little gap in record
• Like a sound argument
• Like a well-armed fort
• Valid
• Can be maintained
• Number clever enough for game show

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Tenable \Ten"a*ble\ (t[e^]n"[.a]*b'l), a. [F. tenable, fr. tenir to hold, L. tenere. See Thin , and cf. Continue , Continent , Entertain , Maintain , Tenant , Tent .] Capable of being held, maintained, or defended, as against an assailant or objector, ...

Wikipedia Word definitions in Wikipedia