A solo = killing the enemy flagcarrier + usually another player of their team (the one who is R) yourself, while you carry the flag and score the point for your team right after.
It is you only who scored that point for your team, basically.

An example:


[16:08:03] *** VegitoCC roasted Suè [VS]
[16:08:03] *** VegitoCC roasted Ashurna>MV<
[16:08:04] -FDC-D@Ru0M: 3HK
[16:08:05] *** VegitoCC roasted -t3>Pisanek
[16:08:05] *** -t3>Pisanek lost the Blue Flag
[16:08:05] *** VegitoCC made the score
[16:08:05] *** Blue Team scored a point
[16:08:06] -FDC-D@Ru0M: YAY
[16:08:06] *** TW-CDF captured the flag
[16:08:06] Suè [VS]: gg
[16:08:07] VegitoCC: well doen
[16:08:09] -FDC-D@Ru0M: TRIPLE