it is also in the non-computer world, something you do around halloween.there is a whole rhyme that goes with it, but essentially you fill up small treat bags (2)with candy and little treats and somesort of sign or decal and the rhyme poem.You ring someones door bell(usually around dusk or early evening) and you leave the treat on their doorstep.Then that person would put the decal on their door to show they have been Boo'ed and they have to do it to 2 more people and so on.It is alot of fun and our neighborhood usually starts this around OCt 1st.It is better to be one of the first to be boo'ed since you are not supposed to boo the same house 2x(hence the decal /sign on the door).