Hair gel: A term which describes cum ejaculated onto hair. This usually happens as the aftermath of many types of Blow jobs.
Alternatively, as in the case of Ben Stiller in the movie "Something About Mary", where the ejaculate ended up in the original masturbater's hair, and was subsequently used as actual hair gel.
Cum does dry to a rigid state, as evidenced by the state of a tissue several hours after use as a post-coital cleanup item. Therefore, it is entirely possible to use cum as a hair gel if the desired effect is cementing the hair style in place.