In search a goal state is one of a number of states of the system that are seen as an acceptable solution. In some cases this may mean any state that satistfies constraints (a feasible solution. In other cases we are looking for a goal state that is best (an {{optimal solution) according to some measure such as a fitness function. On between we may be happy with goal stats that are 'good enough' (satisficing).
Used in Chap. 3: page 26; Chap. 4: pages 36, 38, 39, 41, 42, 43, 44, 48, 49, 55; Chap. 15: pages 222, 223, 235; Chap. 22: page 346