All references that I've come across list "absorb" only as a transitive verb, yet I find it used commonly in the medical and advertising community intransitively. For example, "Our vitamin C absorbs more quickly". I want to ask, what does it absorb, as absorb is a transitive verb needing an object: "Our brand of paper towel absorbs liquid more quickly than brand X."--edited. On the other hand a word such as "assimilate" can be used both transitively and intransitively. Whether a word is transitive only or both transitive and intransitive seems to be rather arbitrary, and and I find people taking liberties to speed the process of making transitive verbs into intransitive verbs, for their convenience, I assume; so rather than say the vitamin C is absorbed into the bloodstream they will say the vitamin C absorbs into the bloodstream, which is grammatically incorrect. Adding "into the bloodstream" does not make it any less an intransitive usage in the latter case.