Refers to a yaoi fanfic or artwork containing a relationship between the Gundam Wing characters Heero and Duo. If sexual, Heero is the dominant partner and Duo the submissive. This might have equivalents to other anime series, but Heero x Duo is the only one I know.
1x2, 3x4, 5x no one because we hate Wufei.
An abbreviation of two pilots from the popular japanese anime Gundam Wing, heero and duo. It is mostly used in yaoi fanfiction and fanart by fans for the romance between the characters. There are various of these pairings, for starters, the meanings:
1 > heero 'reference for leader of the gundam pilots'
2 > duo 'means two in italian (i think)
3 > trowa 'trois = three in french'
4 > quatre 'means four in french'
5 > wufei 'if you say this name, you can hear five somehow'
6 > zechs 'means six in german'
13 > treize 'means thirteen in french'
the most common pairings are 1x2, 1x2x5, 3x4, 6x13, 13x5
1X2 is not the same without wufei T_T
gundam wing yaoi/shounen-ai fanwork term. it means HeeroxDuo.