To say a rude or slick comment towards another person with little or no one else catching the insult except who it was directed towards.

When your so pissed off from losing multiple amount of games that you play worse and worse till your so pissed you begin leaning over your keyboard screaming over every little mistake you make and complaining about gaming imbalances

(Common in Starcraft II)

to talk trash about a friend or aquaintance, to publicly denounce or disrespect. When throwing shade it's immediately obvious to on-lookers that the thrower, and not the throwee, is the bitcy, uncool one

To hate on someone for acting a fool.