Confound/kənˈfaʊnd/ Definition 1 of 5Pro Tip 1/2Unexpected Behavior Use 'confound' when someone acts against what others predict or foresee. She confounded her critics by donating her entire fortune to charity. Pro Tip 2/2Sudden Surprise Conveys a strong and often immediate feeling of surprise or disbelief. His ability to solve complex problems so quickly completely confounded me.