1. A situation in which one object is hit by another one: During their game outside on the lawn, the two boys hurt themselves by colliding together, an act of impaction!
2. A bodily disorder in which the faces are wedged tightly in the lower colon: After a postmortem was done, the specialist diagnosed the horse to have had an impaction, or a solid immobile bulk of stool, due to dehydration and colitis in the stomach.
3.The condition of being pressed firmly or tightly together: The impaction of earwax, or cerumen, against the eardrum caused tinnitus in Adam's ears.
4. A situation of a tooth being crowded in its socket and which cannot erupt in a normal way: When Martin went to the dentist's for a regular checkup, his dentist diagnosed an impaction in Martin's upper row of teeth and told him that it had to be taken care of right away.

An accumulation of hardened or inspissated feces (thickened, dried, or made less fluid by evaporation or absorption of liquid components) in the rectum or sigmoid colon that the individual is unable to move out by defecation.

Diarrhea may be a sign of fecal impaction, since only liquid material is able to pass the obstruction.

Sometimes fecal impaction may cause urinary incontinence because of pressure on the bladder.

People who are dehydrated; nutritionally depleted; on long periods of bed rest; receiving constipating medications; such as, iron or opiates; or undergoing barium radiographic studies are at risk of developing fecal impaction.

Prevention includes adequate ingestion of bulk food, fluids, exercise, regular bowel habits, privacy for defecation, and occasionally stool softeners or laxatives.