<p><strong>Adjective</strong></p><ul><li>Showing a decline or deterioration of physical strength or mental functioning, especially short-term memory and alertness, as a result of old age or disease.</li><li>Of or belonging to old age or aged persons; gerontological; geriatric.</li><li>(Of topographical features) Having been reduced by erosion to a featureless plain that stands everywhere at base level.</li></ul><p><strong>Noun</strong></p><ul><li>A senile person.</li></ul>