acyclic

from WordNet (r) 3.0 (2006)

acyclic
    adj 1: not cyclic; especially having parts arranged in spirals
           rather than whorls [ant: {cyclic}]
    2: having an open chain structure [syn: {acyclic}, {open-chain}]
       [ant: {cyclic}]

from The Collaborative International Dictionary of English v.0.48

Acyclic \A*cyc"lic\, a. [Pref. a- not + cyclic.]
   Not cyclic; not disposed in cycles or whorls; as:
   (a) (Bot.) Of a flower, having its parts inserted spirally on
       the receptacle.
   (b) (Org. Chem.) Having an open-chain structure; aliphatic.
       [Webster 1913 Suppl.]