That magical and poorly-understood state between a flaccid and fully erect penis. A jaybird exhibits a trademark curved and drooping demeanor. It typically occurs in the arousal phase during which the penis transitions from its common limp state of being to a full hard-on.
I was unsure about our first time together, but when I disrobed and she saw my glorious jaybird, the look in her eyes told me it was on.
I was rolling commando, as I always do. My jaybird got caught in my zipper. It hurt like hell.