WiFi's are made when the two people performing are too far away to physically connect a high five and instead perform the motions of one without actually touching.
The instigator should announce 'WiFive!' before acting it out so as to not cause confusion.
WiFi's may or may not be accompanied by a 'whoopish' noise in order to make the gesture more realistic.
If your really nerdy and someone fails to realise the WiFive or tries to reach for a real high five and fails then they may be taunted by everyone around them making the old 56Kb dial up noise really loud in their face.
Booooooooo ba da da ba ba da da ba da ba da bee Bee bada biiiir beeeeeeeeeee aa eeeeeeeeeeEEEEEEEEEEEEEEEEEEE bir BIR bow dow bow dow bow EEEEEEEECKKKKKKKKKKKKKKKKKKK AAAAACKKKKKKKKKKKKKKKKKKK AAAAAAAAAAAAAAAAAAAAAAAGH PHffffffffffFFFFFFFFFFFFFFFFFFT
Mix of "wireless" and "high-five", hence "wi-five", (wireless high-five)
Eric (in response): You need to chill with that nano shit, son
which is the true definition of a high five done when two people are too far apart to physically engage in a "high five"
Mack: High five!
John: You are too far away...
John: NO! Air five! hells yeah....