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1.
noun: The condition, state, or sensation of sexual excitement accompanied by increased pulse, coursing hormones (such as epinephrine) in the bloodstream, and neurotransmitters (such as phenylalanine) in the brain, that precedes an male erection of the penis, or female erection of the clitoris.
Having read and re-read the amorous note from Frenchy, Allyson's prerection caused her to grow moist.
by Achilles Murat II November 09, 2011
 
2.
1. The stage of erection in a penis before it has reached full hardness.

2. The mental stage of arousal before a physical arousal change in the hardness of a penis.
1. John- "Dude.. I don't wanna stand up, I have a prerection and it might show."
Mike- "Me too!"

2. John- "Dude.. I had such a prerection when I was looking through that playboy, but my dad walked in on me.. Needless to say I didn't achieve boner-ness.
Mike- "That blows."
by Reklaw Yeoj May 13, 2011