It means light and is the opposite of Yami... It can also refer to the lighter side of one.
Yugi is Yami's light side aka hikari.
ayon kay Whispering Hope ika-12 ng Agosto, 2003
2 more definitions
The other half, true love
Rumaru is Ess' hikari.
ayon kay He-Kar-Ri ika-07 ng Setyembre, 2003
word used to describe ghesia woman activists who have the tendancy to PMS all over other minorites of Brown oR CaraMel skin shade. Also known to give boys the "why the fuck are you still breathing"look.
Yo Did you just see that look Hikari gave me...i think i just shat myself.
ayon kay Gerald from Hey Arnold ika-13 ng Abril, 2008