Can apply to both individuals and groups.

For individuals it is when someone shows their appreciation Facebook post by BOTH using the thumbs up function as well as mentioning how much they like the post in a comment.

Alternatively, it refers to excessive "likes" by many people on the same post (approx 10 or more).
Tegan's FB Post: @thedaleks when will you learn? (updated via Twitter)

*Megan and 15 other people like this*

Megan's comment: LOVE THIS!!

... Later that day...

Megan: Tegan I saw that post you did about the Daleks on FB - hilarious. I like-jaculated all over it.

Tegan: Yeah, 15 people liked it! I love it when people like-jaculate on my Facebook.
by MegsGirds October 13, 2011
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