You can find most popular coin collecting phrases in this coin glossary.
incuse - the part of a coin's design that is pressed into the surface. Opposite of relief. Example: the $2 1/2 and $5 Indian US gold coins are incuse design. Rather than the design being raised up off of the surface of the coin, it is pressed into the metal. See "reeded edge" and "lettered edge" ingot - see "bars"
Ike dollar - see Eisenhower dollar
inscription - the words stamped (written) on a coin
intrinsic value - the value of the precious metal that a coin is made of. Often called "bullion value". Not to be confused with "face value".
investment grade - used to indicate a high grade of coin that might make a good investment.