Derived from Spit-Roast.
Two lads looking at sexy girls flirty profile on facebook and both poke her at the same time. You can then post on her comments that she's just been spit-poked :-P
'While at work browsing Facebook on our mobiles'
"Hey Dave" you seen this chick on facebook? wow! she's hot dude lets give her a spit-poke so she knows it.
(she knows who you are and that your both looking at her sexy pictures and she loves the attention of being Spit-Poked)