senior moment(노망)

have a senior moment. 

to forget something in a way that is thought to be typical of people who are old.

나이가 드신 사람들처럼 자주 잊어버리거나

(말 그대로 노망) /

A lapse of memory, logic or mental function which is atypical or unusual. The individual suffering the event, may not necessarily be advanced in age, although senior citizens are more likely to experience an occurrence.

(http://ko.urbandictionary.com/define.php?term=senior%20moment)

치매 걸린 사람처럼 이상한 행동을 했을 때도 사용함.

Mom had a "senior moment" yesterday when she poured laundry detergent into the dryer.

(http://ko.urbandictionary.com/define.php?term=senior%20moment)

[엄마가 어제 노망났다봐.. 세탁기 세제를 건조기에 부었어..]

<참고: urban dictionary: 성적이고 저속한 표현을 많이 알려주는 사전. 슬랭을 배우기에 좋은 사이트>