forgetful
for-get-ful
adjective
Tending to forget things easily or having a poor memory.
"Grandad's getting a bit forgetful these days."
Thesaurus
Synonyms: inattentive, oblivious, unretentive, short, unmindful, mindless, amnesic, amnesiac
Antonyms: aware, long, mindful, recollective, retentive, tenacious