Merriam-Webster Collegiate Dictionary - ponder

 verb  (~ed; ~ing)  Etymology: Middle English, from Middle French ~er, from Latin ~are to weigh, ~, from ~-, pondus weight — more at pendant  Date: 14th century  transitive verb  1. to weigh in the mind ; appraise ~ed their chances of success  2. to think about ; reflect on ~ed the events of the day  intransitive verb to think or consider especially quietly, soberly, and deeply  • ~er noun Synonyms:  ~, meditate, muse, ruminate mean to consider or examine attentively or deliberately. ~ implies a careful weighing of a problem or, often, prolonged inconclusive thinking about a matter ~ed the course of action. meditate implies a definite focusing of one's thoughts on something so as to understand it deeply meditated on the meaning of life. muse suggests a more or less focused daydreaming as in remembrance mused upon childhood joys. ruminate implies going over the same matter in one's thoughts again and again but suggests little of either purposive thinking or rapt absorption ruminated on past disappointments.