A significantly close sibling, usually a year or two apart. Most commonly misspelled as "Smiffey", and can be shortened to "Smiffz". A "Smiffy" tends to use spaces in between punctuated smiley faces and before/after punctuation.
Smiffy, you are the best big sister in the entire world, let's take a profile picture for our Facebook profiles to show everyone how close we are!
by TheRealSmiffy April 26, 2011