GMAT Vocabulary Flash Cards @ englishpdf.com and englishteststore.com File 353 instructive (adj) Conveying knowledge insubordinate (adj) disobedient to authority insufficiency (n) Inadequacy insufficient (adj) Inadequate for some need, purpose, or use insular (adj) Pertaining to an island insularity (n) having the characteristics of an island insulate (v) To place in a detached state or situation insuperable (adj) Invincible