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blot (one's) copy book

To tarnish, damage, or ruin one's reputation by behaving badly or committing some mistake or social transgression. Refers to a child's copy book, the blotting (staining with ink) of which ruins one's work. Primarily heard in UK. The local councilor blotted his copy book when it came to light that he had accepted bribes to allow unregulated development projects to go ahead. I really blotted my copy book when I spilled my drink on the visiting dignitary last night.
See also: blot, book, copy

blot your copybook

If you blot your copybook, you damage your reputation by doing something wrong. Their relationship had been so perfect. Until he'd blotted his copybook with Susan, that is. Note: You can also say that there is a blot on your copybook. In fact, just about the only blot on his copybook so far was a missed penalty against Arsenal 10 days ago. Note: In the past, schoolchildren had `copybooks'. These were books of examples of handwriting, with spaces for the children to copy it.
See also: blot, copybook

blot your copybook

tarnish your good reputation. British
A copybook was an exercise book with examples of handwriting for children to copy as they practised their own writing.
See also: blot, copybook

blot your ˈcopybook

(old-fashioned, informal) spoil a previously good record: He paid back the money he had stolen, but he had blotted his copybook and couldn’t hope for promotion.A copybook was an exercise book with printed examples of good writing for children to copy. If you blotted it, you accidentally spoiled it by making a mark with ink on it.
See also: blot, copybook
References in periodicals archive ?
Environment Division SELECT/ASSIGN statements and Data Division FD statements are generated for up to four (4) input/output files and can include expanded copybooks is the user chooses to upload them via the online form.
The third scene of the copybook consists of talk about the Keogh-Bennett fight and about Irish sports.
But though we had plenty of money There was nothing our money could buy And the gods of the copybook headings said 'If you don't work you die'.
COLWYN BAY 1 BRACKLEY 1 COLWYN BAY blotted Brackley's copybook to earn a notable point as they relieved the Blue Square Bet North leaders of their 100 per cent record.
But even he blots his copybook when Laura's waters break in the middle of a shopping centre.
Jose Mourinho admits his focus is on the weekend and he will not be unduly concerned if his team blot their European copybook.
It's a blot on the copybook of Taoiseachin-waiting Enda Kenny - the problem is right smack in the middle of his Mayo constituency.
He blotted his copybook by paying tribute to Gordon Brown's "30 years of public service".
Reigning world champion Hamilton set the third-quickest time on the fifth day of the multi-team test but blotted his copybook when a sudden gust of wind sent the Briton's car plunging backwards off the track and into a tyre barrier.
Bridgend blotted their copybook 15 minutes from the end when Haydn Flemming was sent off following a reckless tackle that was out of keeping with the sportsmanship of the tie generally.
00pm) Rachel isfrustrated when two brothers both offer conflicting versions of the stabbing of a drug dealer and Leon blots his copybook with his boss once more through his determination to help, and Will gets a chance to impress Neil.
The latest blot on Shoaib's copybook was when he criticised the Pakistan Cricket Board after missing out on one of the top contracts to play for the national team.
ANDY MURRAY blotted his copybook with several verbal volleys of expletives during defeat to Nikolay Davydenko in Dubai but at least he didn't sink as low as Roger Federer.
Kate Moss might have blotted her copybook with H & M and other big names, but Yves Saint Laurent is standing by the supermodel for its new Opium campaign - so we'll be seeing her soon.
Ducati Fila rider Hodgson blotted his copybook when he missed out on pole position for the first time this season but made up for it in fine style with victories in both races to stretch his lead at the top of the title standings to 46 points.