- an arm off of a larger body of water (often between rocky headlands)

1. A passage by which an inclosed place may be entered; a place of ingress; entrance.

"Doors and windows, inlets of men and of light." -- Sir H. Wotton.

2. A bay or recess, as in the shore of a sea, lake, or large river; a narrow strip of water running into the land or between islands.

3. That which is let in or inlaid; an inserted material.

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Inlet is also used adjectively, as in inlet pipe, inlet valve, etc.