what is a good definition for induced pluripotent stem cell?

"Induced" means that the stem cell was created from something that wasn't originally a stem cell, or at least not a pluripotent one ("pluripotent" means it can turn into multiple types of cells). The only time you'd do this is to create a pluripotent stem cell from an adult - most adult cells are differentiated already, and therefore can only reproduce to make copies of themselves, or turn into a type of cell very similar to themselves (if they can reproduce at all). Even adult stem cells are differentiated - a stem cell in the blood will only make more blood cells, and a skin stem cell will only make more skin cells. "Inducing" a cell in this context means you are turning back the clock, in a way - you are doing something to that skin cell to give it back the ability to turn into a kidney cell, or a muscle cell, or a neuron, etc.
In contrast, embryonic stem cells are inherently pluripotent - an embryo starts out as a single cell, and that single cell has to divide and eventually give rise to every type of cell in the body. Therefore, an embryonic stem cell already has the ability to turn into any type of cell in the body given the correct chemical/biological signals, and does not need to be induced to become pluripotent.