The quality by which a penis is described in terms of how prime it is for being given a blowjob, or to be sucked at all. (factors include: length, width, etc.) *can be described in quantitative or qualitative terms*
Franklin: Thomas, how was your date with Megan last night?
Thomas: It went wonderfully, she sucked my dick.
Franklin: I'm not surprised, your dick's suckability is OVER NINE-THOUSANDDDDD!!1