showing a decline or deterioration of physical strength or mental functioning, esp. short-term memory and alertness, as a result of old age or disease.

of or belonging to old age or aged persons; gerontological; geriatric.

Physical Geography . (of topographical features) having been reduced by erosion to a featureless plain that stands everywhere at base level. Compare peneplain .

a senile person.

adjective

alert , well , young

adjective

aged , ancient , anile , decrepit , doddering , doting , enfeebled , feeble , imbecile , infirm , in second childhood , old , senescent , shattered , sick , weak , anecdotal , caducous , feebleminded , superannuated , venerable