erratic — English Dictionary

Adjective

1. Unsteady, random; prone to unexpected changes; not consistent.

   Synonyms

   mercurial

   Examples

   Henry has been getting erratic scores on his tests: 40% last week, but 98% this week.

   When we found you on the street, your behavior was all erratic and it seemed like you were having a panic attack.

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   The V-2's directional system was notoriously erratic. In May 1947, a V-2 launched from White Sands Proving Ground headed south instead of north, missing downtown Juarez, Mexico, by 3 miles.

2. Deviating from normal opinions or actions; eccentric; odd.

   Examples

   erratic conduct

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   Investigators were careful not to rule out Bryce’s erratic behaviour in his final days, including the giveaways, the sudden breakup, and the hours spent parked by the side of the freeway. These factors pointed to a mental health crisis severe enough that he wanted to disappear.

Noun

1. A rock moved from one location to another, usually by a glacier.

   Examples

   The term for a displaced boulder is an erratic, but in the nineteenth century the expression seemed to apply more often to the theories than to the rocks.

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   During the last ice-age, massive stones were carried for miles by the scouring glaciers, only to be left, like passengers at the end of the line, when the glaciers retreated. Stranded in their new surroundings with rocks with which they share no common geology, their out-of-place-ness is evoked by their name: “erratics”.

2. Anything that has erratic characteristics.

Adjective

1. liable to sudden unpredictable change

   Synonyms

   ficklemercurialquicksilver

   Examples

   erratic behavior

   fickle weather

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   mercurial twists of temperament

   a quicksilver character, cool and willful at one moment, utterly fragile the next

2. having no fixed course

   Synonyms

   planetarywandering

   Examples

   an erratic comet

   his life followed a wandering course

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   a planetary vagabond

3. likely to perform unpredictably

   Synonyms

   temperamental

   Examples

   erratic winds are the bane of a sailor

   a temperamental motor: sometimes it would start and sometimes it wouldn't