It is the erect blood filled penis. brought on my sexual arousion. the average male gets 3 a night while your sleeping. also known as an erection, stiffy, chubby, hard on

example… that guy would stick his boner in anything with a hole
 

Below are more examples of the usage of  ‘Boner’ ..

Boner Pills
Slang term for any number of erectile dysfunction medications, such as Viagra, Cialis and Levitra.

Him: “This has never happened to me before.”
Her: “Well, maybe you should start taking boner pills.”

Boner-block
When you try to jack off but you start to lose your boner because you can’t think of anything or you lose your horniness.

John tried to jack off but he failed because he got boner-block.

Boner Limbo
The state in which a man does not have a full erection, but his penis is slightly harder than the norm. In this state, it is easy for the penis to become fully erect as a result of things that would not normally cause a boner, such as walking.

“Yo man, get your ass out of bed.”
“Can’t. I’m in boner limbo.”

Boner jam 
exceptional scene culled from a pornographic film; the penultimate segment of a pornographic work popularized by the film ‘the 40-year old virgin’ in which he is given a tape of sacred porno moments called “boner jams ’03″.

the second scene of jenna jameson’s last film is all boner jam.

Boner in a china shop 
twist on the old idiom to describe yourself or someone with a large penis. It is hyperbole in most respects but also speaks for the extreme close quarters that one encounters in some china shops. It could also be used sarcastically if someone is known to have a penis of below the average size.

Jim- “Hey Jane i saw your boyfriends wang in the shower at the gym last week, im not surprised that he’s been a little shy in the bedroom.”
Jane- “Do you mean its small or something?”
Jim- “Lets just say he wouldnt have a problem having a boner in a china shop.”

Boner cat 
The cat that always seems to show up, purring, whenever you have a boner, and proceeds to watch you have sex, receive a blow job, masturbate, etc. (Includes NARBs)

You: Oh look, there’s the cat watching us again.
Your wife: You know we can’t have sex without our beloved boner cat present.
 
Boner Wedgie 
When your boner is so hardcore that it stretches your underwear taut, delving right into your crack.

My Boner Wedgie has been hounding me for hours.

and so on..