The group CH2=CHCH2 (allyl) and derivatives formed by substitution. The term 'allylic position' or 'allylic site' refers to the saturated carbon atom. A group, such as –OH, attached at an allylic site is sometimes described as 'allylic'.
PAC, 1995, 67, 1307. (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1315 [Terms] [Paper]