Obstáculum, obstáculi, n. g. pen. cor. Plaut.An obstacle, impediment, or let.
Lewis and Short: Latin dictionary
ob-stācŭlum, i, n. [obsto], a hinderance, obstacle (post-class.; cf. impedimentum): teneris et rarioribus parcit (fulmen), quia transitu patente minus obstaculum invenit, Sen. Q. N. 2, 52, 1: rumpere obstacula, Prud. Ham. 601; App. Flor. p. 361, 11; Arn. 2, 62; Amm. 17, 3.—In plur., of mountains, Amm. 21, 10.