Noun

(en noun)

The act of librating.

(astronomy) The apparent wobble or variation in the visible side of the Moon that permanently faces the Earth, allowing observers on Earth to see, over a period of time, slightly more than half of the lunar surface.

(by extension) A similar rotational or orbital characteristic of some other celestial body.

Noun

(-)

A fearful state; a state of hesitation or concern.

I decided, with considerable trepidation , to let him drive my car without me.

* 1929 , , Chapter VII, Section vi

She opened the drawing-room door in trepidation . Would she find Esther drowned with her head in the goldfish bowl, or hanged from the chandelier by her stay-lace?

* {{quote-news

, year=2011 , date=December 10 , author=Marc Higginson , title=Bolton 1 - 2 Aston Villa , work=BBC Sport citation , page= , passage=The Midlanders will hope the victory will kickstart a campaign that looked to have hit the buffers, but the sense of trepidation enveloping the Reebok Stadium heading into the new year underlines the seriousness of the predicament facing Owen Coyle's men.}}

An involuntary trembling, sometimes an effect of paralysis, but usually caused by terror or fear; quaking; quivering.

(astronomy, obsolete) A libration of the starry sphere in the Ptolemaic system; a motion ascribed to the firmament, to account for certain small changes in the position of the ecliptic and of the stars.