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A variant on the word "fluctuation", commonly used in the world of economics to identify irregular/varying market movements. However, this term is used specifically in reference to sexual targets of one's liking. In other words, "fucktuation," defines the irregular change in taste of men and/or women when put into a sexual connotation.
1) "Yea, seems like Clinton has taken a liking towards younger girls now."
"I dunno man...he used to date older women, maybe he's going through a fucktuation."

2) "Yo bro, should I go for the younger or older chick tonight? I can't decide dude..."
" Make up your fucking mind and stop fucking fucktuating."
by Andrew Lui May 22, 2008
When you or someone else fucks up a situation.
Shawna had a fucktuation when she banged her knee on the counter.
by BBBBBBBBDDDDAAAA November 02, 2012
Inconsistency in one's sex life.
A: I used to get laid all the time, but I never do anymore...
B: I'm sure it'll be fine, life is always full of fucktuation.
by ultrahedgehog February 23, 2014