Unsearchable

Vine's Expository Dictionary of NT Words

1: Ἀνεξεραύνητος (Strong'S #419 — Adjective — anexeraunetos | anexereunetos — an-ex-er-yoo'-nay-tos )

a, negative, n, euphonic, ex (ek), "out," eraunao, "to search, examine," is used in  Romans 11:33 , of the judgments of God.

2: Ἀνεξιχνίαστος (Strong'S #421 — Adjective — anexichniastos — an-ex-ikh-nee'-as-tos )

with the same prefixes as in No. 1, and an adjectival form akin to ichneuo, "to trace out" (ichnos, "a footprint, a track"), is translated "unsearchable" in  Ephesians 3:8 , of the riches of Christ; in  Romans 11:33 , "past tracing out," of the ways of the Lord (cp. No. 1, in the same verse). The ways of God are the outworkings of His judgment. Of the two questions in  Romans 11:34 , the first seems to have reference to No. 1, the second to No. 2. See Find , Note (3), Trace.

King James Dictionary

Unsearchable a. unserch'able. That cannot be searched or explored inscrutable hidden mysterious.

The counsels of God are to us unsearchable.

Webster's Dictionary

(a.) Not searchable; inscrutable; hidden; mysterious.