Lewis & Short

ob-structĭo, ōnis, f. [obstruo], a building before or against, a closing up by building, a blocking up.

  1. I. Lit. (post-class.): corporum, Arn. 2, 63.
  2. II. Trop., an obstruction, a barrier: haec obstructio non diuturna est, Cic. Sest. 9, 22.