1. [adj]  intensifying by augmentation and enhancement
2. [adj]  increasing or having the power to increase especially in size or amount or degree; "muscle-building exercises"

AUGMENTATIVE is a 12 letter word that starts with A.

1. \Aug*ment"a*tive\, a. [Cf. F. augmentatif.]
   Having the quality or power of augmenting; expressing
   augmentation. -- {Aug*ment"a*tive*ly}, adv.
   
   

2. \Aug*ment"a*tive\, n. (Gram.)
   A word which expresses with augmented force the idea or the
   properties of the term from which it is derived; as, dullard,
   one very dull. Opposed to {diminutive}. --Gibbs.