From BiblePortal Wikipedia

Vine's Expository Dictionary of NT Words [1]

A — 1: Ἀδύνατος (Strong'S #102 — Adjective — adunatos — ad-oo'-nat-os )

from a negative, and dunatos, "able, strong," is used (a) of persons,  Acts 14:8 , "impotent;" figuratively,  Romans 15:1 , "weak;" (b) of things, "impossible,"  Matthew 19:26;  Mark 10:27;  Luke 18:27;  Hebrews 6:4,18;  10:4;  11:6; in  Romans 8:3 , "for what the Law could not do," is, more lit., "the inability of the law;" the meaning may be either "the weakness of the Law," or "that which was impossible for the Law;" the latter is perhaps preferable; literalism is ruled out here, but the sense is that the Law could neither justify nor impart life.

A — 2: Ἀνένδεκτος (Strong'S #418 — Adjective — anendektos — an-en'-dek-tos )

signifies "inadmissible" (a, negative, n, euphonic, and endechomai, "to admit, allow"),  Luke 17:1 , of occasions of stumbling, where the meaning is "it cannot be but that they will come."

B — 1: Ἀδυνατέω (Strong'S #101 — Verb — adunateo — ad-oo-nat-eh'-o )

signifies "to be impossible" (corresponding to A, No. 1), "unable;" in the NT it is used only of things,  Matthew 17:20 , "(nothing) shall be impossible (unto you);"  Luke 1:37 . AV "(with God nothing) shall be impossible;" RV, "(no word from God, a different construction in the best mss.) shall be void of power;" rhema may mean either "word" or "thing" (i.e., fact). In the Sept. the verb is always used of things and signifies either to be "impossible" or to be impotent, e.g.,  Genesis 18:14;  Leviticus 25:35 , "he fail;"  Deuteronomy 17:8;  Job 4:4 , "feeble;"  Job 42:2;  Daniel 4:6;  Zechariah 8:6 .

King James Dictionary [2]

IMPOSS'IBLE, a. L. impossibilis in and possibilis, from possum, to be able.

1. That cannot be. It is impossible that two and two should make five, or that a circle and a square make five, or that a circle and a square should be the same thing, or that a thing should be, and not be at the same time. 2. Impracticable not feasible that cannot be done.

With men this is impossible but with God all things are possible.  Matthew 19

Without faith it is impossible to please God.  Hebrews 11

There are two kinds of impossibilities physical and moral. That is a physical impossibility, which is contrary to the law of nature. A thing is said to be morally impossible, when in itself it is possible,but attended with difficulties or circumstances which give it the appearance of being impossible. See Possible, Practicable and Impracticable.

Webster's Dictionary [3]

(1): ( n.) An impossibility.

(2): ( a.) Not possible; incapable of being done, of existing, etc.; unattainable in the nature of things, or by means at command; insuperably difficult under the circumstances; absurd or impracticable; not feasible.

International Standard Bible Encyclopedia [4]

im - pos´i - b ' 50 (verb ἀδυνατέω , adunatéō  ; adjective ἀδύνατος , adúnatos ): "To be impossible" is the translation of adunateō , "to be powerless," "impotent" (  Matthew 17:20;  Luke 1:37 , the Revised Version (British and American) "void of power") adunatos , "powerless," etc., is translated "impossible"  Matthew 19:26;  Mark 10:27;  Luke 18:27;  Hebrews 6:4 ,  Hebrews 6:18;  Hebrews 11:6; "impossible" in  Hebrews 6:4 is in the Revised Version (British and American) transferred to   Hebrews 6:6 ); anéndektos , "not to be received" or "accepted," is also translated "impossible" ( Luke 17:1 ). In several of these passages it is affirmed that "nothing is impossible with God," but, of course, this means nothing that is consistent with the Divine nature, e.g. (as  Hebrews 6:18 ) it is not possible for God to lie. So, when it is said that nothing is impossible to faith , the same limitation applies and also that of the mind or will of God for us. But much more is possible to a strong faith than a weak faith realizes, or even believes.