Definition Any object that endangers, hinders or prevents movement in or under the water or in the air, e.g., a reef, a rock, a wreck, a tower, a pinnacle or a mountain peak. (Source: Team) Use For Obstacles (Navigation) Broader Term Navigation (Dcn) Narrower Terms Clearances (Navigation) (Dcnuc) Related Terms (Hierarchical) Navigation processes (Dcnb) Navigational aids (Dcns)