Mayday
1 of 2communications signal
May·day ˈmā-ˌdā 
—used as a distress call in international radio-telephone communications
May Day
2 of 2noun
ˈmā-ˌdā
: May 1 celebrated as a springtime festival and in some countries as Labor Day
Word History
Etymology
Communications signal
French m'aider help me
First Known Use
Communications Signal
1927, in the meaning defined above
Noun
13th century, in the meaning defined above