It is an adjective.
Meaning : achieving little or nothing. It used to indicate when things did not turn out as expected or nothing is achieved even after pouring lots of efforts.
unavailingly - adverb
unavailingness - noun
Synonyms : ineffective, inefficacious, vain, futile, useless, unsuccessful, nugatory, failed, fruitless
Antonyms : effective,successful,fruitful
1)Efforts to track the perpetrators of the crime proved unavailing.
2)It is an unavailing attempt to try make him change his decision as he is a very stubborn person .
3)All her efforts to get admission into this college turned unavailing.
4)The teacher's effort to make the students maintain silence went unavailing.