When not in use, the fins are tucked into special grooves or depressions so that they lie flush with the body and do not break up its smooth contours.

当鱼不使用鱼鳍时，会将它们折叠起来，收回到特殊的沟槽或者凹陷部位；这样鱼鳍就可以与身体保持齐平，以维持它们平滑的外形。

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The table folds up when not in use.

这桌子不用时可以折叠起来。

《牛津词典》

Body.jsp - Not in use.

jsp—不再使用。

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Jane says she does not use any preservative chemicals in her products, so they only last about two or three weeks.

VOA: special.2010.02.17

At each cross-section, people are either willing to use a certain sign in a certain way or they're not.

在每一个横街面上，人们可以自由的,以自己的方式使用符号。

耶鲁公开课 - 文学理论导论课程节选

and say, "You've not checked it properly. We are in England, use the English language."

然后说，“你没有正确地检查它，我们在英国，请用英式英语。”

美式英语和英式英语 - SpeakingMax英语口语达人

Shades operating by wall-mounted controls disappear into a recessed ceiling pocket when not in use.

WSJ: Sheer Curtains, Solar Shades Are Popular Window Treatments

Otherwise, the idea here is to park the mouse on its dock when not in use.

ENGADGET: Mobee's inductive Magic Charger for Apple's Magic Mouse really is magical

The LCD screen can also be flipped closed for protection when not in use.

ENGADGET: Nikon intros flagship Coolpix P7700 for prosumers, diminutive Coolpix S01 for fashionistas