dangerously fast (adjective) breakneck: extremely fast
Sinonime: acceptable, admissible, allowable, condonable, defensible, excusable, fair, fit, forgivable, lawful,
legit,
legitimate, licit, logical, pardonable,
probable, proper, reasonable, remissible,
right, rightful,
sound,
suitable, tenable, understandable, valid, vindicable, warrantable
Antonime: unjustifiable,
unreasonable,
unwarranted