WordNet sense 1 (capable of being influenced or formed):

pliant

WordNet sense 2 (easily impressed or influenced):

impressionable

WordNet sense 3 (capable of being molded or modeled (especially of earth or clay or other soft material)):

fictile, moldable

WordNet sense 4 (capable of resuming original shape after stretching or compression; springy):

elastic

WordNet sense 5 (forming or capable of forming or molding or fashioning):

formative, shaping

WordNet sense 6 (constructing or tending to construct or improve or promote development):

constructive