i large group/amount of something or people
fucking hell there is 'a nation' of jews out there!
A huge concert series by Avex Trax that showcases their hottest stars; including Ayumi Hamasaki, BoA, & Koda Kumi. This usually lasts for about a month in the summer, and it visits many major cities throughout Japan.
I can't wait to see Ayumi Hamasaki at A Nation this year!