1. A dock employing floodgates to keep water level constant during tidal variations.

2. A harbor for small craft.

An open-top vessel with relatively low sloping sides for holding liquids.

1. A low-lying area, wholly or largely surrounded by higher land, that varies from a small, nearly enclosed valley to an extensive, mountain-rimmed depression.

2. An entire area drained by a given stream and its tributaries.

3. An area in which the rock strata are inclined downward from all sides toward the center.

4. An area in which sediments accumulate.

The mouth of a sprue in a gating system of castings into which the molten metal is first poured.

Deep portion of sea surrounded by shallower regions.