1. The keeping in the body of what normally belongs there, especially food and drink in the stomach. 2. The keeping in the body of what normally should be discharged, as urine or feces. 3. Retaining that which has been learned so that it can be used later as in recall, recognition, or, if retention is partial, relearning. 4. Resistance to dislodgement. 5. In dentistry, a passive period following treatment when a patient is wearing an appliance or appliances to maintain or stabilize the teeth in the new position into which they have been moved.