Greek: αδηλος [adêlos] (Adjetive). Not manifest, indistinct, uncertain, obscure.

αδηλος [adêlos] appears 2 times in the NT:

(1) Luke 11: 44
Woe unto you, scribes and Pharisees, hypocrites! for ye are as graves which appear not, and the men that walk over them are not aware of them. - τα αδηλα [ta adêla] Nom. pl. neuter.

(2) 1 Corinthians 14: 8
For if the trumpet give an uncertain sound, who shall prepare himself to the battle? - αδηλον [adêlon] Accus. sing. fem.