Obstacle, obstruction, hindrance, impediment refer to something that interferes with or prevents action or progress. An obstacle is something, material or nonmaterial, that stands in the way of literal or figurative progress: Lack of imagination is an obstacle to one's advancement. An obstruction is something that more or less completely blocks a passage: A blood clot is an obstruction to the circulation. A hindrance keeps back by interfering and delaying: Interruptions are a hindrance to one's work. An impediment interferes with proper functioning: an impediment in one's speech.

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