1) Liable to a lawsuit 2) Readily usable 3) Unjust 4) Worth trying 
• (a.) That may be the subject of an action or suit at law; as, to call a man a thief is actionable.
adj. actionable stands for a case, in which sufficient preliminary evidence or reason exist to make it into a legitimate lawsuit. Apart from set guidelines many a times it is upto the court of law to consider a case as actionable or not, based on prima facie evidence(s) and logical reasoning.
Ac'tion·a·ble adjective [ Confer Late Latin actionabilis . See Action .] That may be the subject of an action or suit at law; as, to call a man a thief is actionable . 
[adj] - affording grounds for legal action
adjective affording grounds for legal action; `slander is an actionable offense`
furnishing ground for a lawsuit. · liable to a lawsuit. · ready to go or be put into action; ready for use: to retrieve actionable copy from a computer.