1the action or process of obstructing movement, progress, or activity, in particular. obstructing or impeding the actions of an opponent in a game, especially (in ball sports) one who does not have control of the ball. Psychiatry the sudden halting of the flow of thought or speech, as a symptom of schizophrenia or other mental disorder. failure to recall or consider an unpleasant memory or train of thought. 2the grouping or treatment of things (e.g., items of data or shades of color) in blocks. the physical arrangement of actors on a stage or movie set.