Boosting is the general term for improving an initially poor or weak solution and maijg it better. For example, rone can take a number of different classifiers, each of which is not very accurate on theor own, and combaine them by giving each a "vote" in the final outcome, whuch may be far more accurate than any single classifier on its own. A different form of boosting can be to identify training itms that are consistenly classified poorly and addng weight to them during successive trainining rounds.
Used on Chap. 8: page 161; Chap. 16: page 387; Chap. 22: pages 546, 547; page xxvii