Student or Learner
This is talking about clitoral priapism:
"Priapism does occur, but is a rare condition, as is a lack of clitoral erection."
Does "as is" here mean to define priapism, i.e. priapism = a lack of clitoral erection? My dictionary says "priapism of the clitoris is a rare condition associated with prolonged erection of the clitoris". If it's "prolonged" erection, how can it be "a lack of" erection at the same time?
No. It means priapism is rare, and so is lack of clitoral erection. They are different things, but they are both rare.