5. Literally, anything is immense when it can not be measured; of vast extent.
7. Immortal. Not liable to death.
10. Having no way through (per = through); as, cloth which is impervious to water; waterproof.
14. An impulse is a sudden mental motive or feeling which tends to drive one on to say or do something.
15. Not liable to punishment; freedom from the bad consequences which usually result from an act; as, the magician could eat fire with impunity.
16. In the flesh; as Christ was the incarnate Son of God.
17. Not mild, but harsh and severe; as inclement weather.
18. Not known; under an assumed name; disguised; as a nobleman traveling incognito.
21. A story is incredible when it is not capable of being believed; unworthy of belief.
26. Indent. To cut into points like a row of teeth.