M-day
About Our Definitions: All forms of a word (noun, verb, etc.) are now displayed on one page.
About Our Definitions: All forms of a word (noun, verb, etc.) are now displayed on one page.M–day
noun \ˈem-ˌdā\Definition of M-DAY
: a day on which a military mobilization is to begin
Origin of M-DAY
mobilization day
First Known Use: 1924
Seen & Heard 
What made you want to look up M-day? Please tell us where you read or heard it (including the quote, if possible).
