Constipation so severe that the rectum (and occasionally the sigmoid colon) is blocked with fecal masses.

Some degree of constipation is seen in over 90% of terminally ill cancer patients under palliative care because of immobility, dietary changes, poor fluid intake, and medication (especially opioids).
Fecal impaction is frequently found on rectal examination though the patient may have few symptoms related to it, with the exception of rectal discomfort, abdominal bloating and pain on defecation. The importance of diagnosing and effectively treating it makes rectal examination mandatory in such patients.

Rarely if ever are oral laxatives effective in fecal impaction.
The fecal mass must first be softened with arachis or olive oil per rectum, followed by appropriate enema and only when the rectal mass has been passed can oral laxatives be prescribed.
Manual removal of feces under appropriate sedation is often the kindest and quickest way to help such patients.

Sykes, N. Oxford Textbook of Palliative Medicine, 3rd ed. London. Oxford University Press, 2005. pp. 483-495.