slip a cog

Idioms  

1. Also,. Lose one's ability to reason soundly or make correct judgments, as in She must have slipped a cog or she would never have gone out barefoot in December, or What's the matter with him? Has he slipped his gears? These slangy usages allude to a mechanical failure owing to the cog of a gear or a gear failing to mesh. The first dates from about 1930, the variant from the 1960s.

---

Example Sentences

On the second round, he seemed to slip a cog on the par-three fifth hole.

From Time Magazine Archive

They will go on prospering; there is no further reason why he should bend a wire, slip a cog, or delay the hurrying wheels.

From Floyd Grandon's Honor by Douglas, Amanda Minnie

I know you can drive like—like you can work algebra, logyruthms, and never slip a cog.

From The Reclaimers by McCarter, Margaret Hill

And would nature allow it to choke up or slip a cog just because a little thing like a worm got tangled in its gearing?

From Quacks and Grafters by Unknown

But Margaret-by-the-day proved an interesting game, if it did slip a cog or two in its development.

From The Girl Scouts at Sea Crest Or, the Wig Wag Rescue by Garis, Lilian