Merriam-Webster Collegiate Dictionary - frustrate

 I. transitive verb  (~d; frustrating)  Etymology: Middle English, from Latin frustratus, past participle of frustrare to deceive, ~, from frustra in error, in vain  Date: 15th century  1.  a. to balk or defeat in an endeavor  b. to induce feelings of discouragement in  2.  a.  (1) to make ineffectual ; bring to nothing  (2) impede, obstruct  b. to make invalid or of no effect Synonyms:  ~, thwart, foil, baffle, balk mean to check or defeat another's plan or block achievement of a goal. ~ implies making vain or ineffectual all efforts however vigorous or persistent ~d attempts at government reform. thwart suggests frustration or checking by crossing or opposing the army thwarted his attempt at a coup. foil implies checking or defeating so as to discourage further effort foiled by her parents, he stopped trying to see her. baffle implies frustration by confusing or puzzling baffled by the maze of rules and regulations. balk suggests the interposing of obstacles or hindrances officials felt that legal restrictions had balked their efforts to control crime.  II. adjective  Date: 15th century characterized by frustration