prerelease

Short definition from Wiktionary

Adjective

1. 1
   Before release.

Noun

1. 1
   A preliminary version of a work, released in advance.
2. 2
   An inadvertent (premature) release of a skiboot from the bindings of a ski, caused by excessive vibration, such as going over an extremely bumpy piste.

Verb

1. 1
   To release in advance