Word familyadjectiveApriliannounApril foolAprilApril Fools' Day
ˌApril ˈFools’ Day (also All Fools’ Day) noun
TRICK/DECEIVEApril 1st, a day when people play tricks on each other 愚人节〔4月1日〕
Examples from the Corpus
April Fools' Day• At first I thought it must be April Fools' Day.• He was indictedApril Fools' Day.• He went to policecollege on April Fools' day, 1970, where he was the beststudent among his intake.• It's a charity thing - something to do with April Fools' Day.