Butylene

noun

2. A hydrocarbon (C4H8) belonging to the olefine series. It exists in three isomeric forms, all of which are gases at ordinary temperatures.
3. Any one of three metameric hydrocarbons, C4H8, of the ethylene series. They are gaseous or easily liquefiable; -- called also butene.
4. the hypothetical divalent radical -(CH2)4-; -- used in combining forms.

   "butylene diamine"

5. Any of three isomeric aliphatic alkenes containing four carbon atoms and one double bond; their polymers are used as synthetic rubber.