IPA: /ˈɒbstəkl/
KK: /ˈɑbstəkl/
Something that blocks or makes it difficult to move forward or achieve something.
The fallen tree was an obstacle on the hiking trail.
Obstacle → It is formed from "ob-" (meaning against) and "stare" (meaning to stand). The word describes something that stands in the way or against progress.
Think of something that stands 'against' ('ob-') your path — that's why an obstacle is something that blocks your way.
No commonly confused words.