Only arguably, and like many things in the Bible it has a bit of leeway for interpretation.

The sin of Onan can be interpreted in two different ways. The first, as Weboji pointed out, is that the sin is the spilling of his seed upon the ground.

The other view, which is my standpoint, is that Onan's sin wasn't the spilling of his seed but the failure of Onan to uphold the levirate marriage that was custom for the time, and mandated per Deuteronomy. Onan failed in his obligation to the law, which is the sin rather than the masturbation. And as far as being unclean, there are a number of things that result in uncleanliness per Judaic law, such as menstruation or childbirth. It's not exclusive to masturbation, and doesn't, necessarily, denote sin.

Buddhism doesn't outright ban masturbation. The third of the Five Precepts only forbids "sexual misconduct," which is quite open to interpretation, to say the least. Surely you'll grant that there is a significant difference between a man (or woman) who masturbates once a day versus someone who does so to the point of excess? If the point of Buddhism is Enlightenment and Nirvana, what is to prevent a person who has a normal sexual appetite who masturbates from walking along that path? There are stricter regulations for monks and nuns and also for certain sects, but there is no strict prohibition against it for the average Buddhist layperson.