The inductive bias of a learning algorithm is the set of assumptions that the learner uses to predict outputs given inputs that it has not encountered—Tom Mitchell
"Inductive bias" refers to your suspicion that if the sun has risen for the last billion days in a row, then it may rise tomorrow as well. Since it is logically possible that the laws of physics will arbitrarily cease to work and that the sun will *not* rise tomorrow, coming to this conclusion requires an inductively biased prior.
- Tom M. Mitchell (1980) (PDF). The need for biases in learning generalizations. http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.120.4179.