The main structural beam along a ship’s bottom, bow to stern.

• A fixed fin or weighted extension under a hull that adds stability.

从船首到船尾贯穿船底的主纵向骨架。

• 位于船体最下方、用于增加稳定性的固定鳍或配重延伸。

A longitudinal member or fixed fin on an airship or aircraft for stability.

• A surface helping the craft hold its course.

用于增加稳定性的飞船或飞机纵向构件或固定鳍面。

• 帮助飞行器保持航向的表面。

The rigid lowest part of an iceberg below the waterline.

• The deep underside of sea ice projecting downward.

冰山在水线下最坚硬、最深的底部部分。

• 海冰向下突出的底面。

In pea-family flowers, the two fused lower petals enclosing stamens and pistil.

• Also called the carina.

蝶形花冠中相连的两枚下部花瓣，包裹雄蕊和雌蕊。

• 亦称龙骨瓣。

A prominent spiral ridge on a shell or whorl.

贝壳或螺旋壳体上的显著螺旋脊棱。

A flat-bottomed cargo boat, especially from northern England.

• Historically used on rivers and canals.

一种平底载货船，尤指英格兰北部的河运船。

• 历史上用于河流和运河。

To keel over; to capsize or tip so the bottom shows.

• By extension, to collapse or faint suddenly.

倾覆；船体翻转以致露出底部。

• 引申：突然倒下或昏厥。