blot one's copybook
Definition of blot one's copybook
: to harm one's own reputation The star football player blotted his copybook by using bad language in an interview.
Word by Word Definitions
: a soiling or disfiguring mark : spot
: a mark of reproach : moral flaw
: a usually nitrocellulose or nylon sheet that contains spots of immobilized macromolecules (as of DNA, RNA, or protein) or their fragments and is used to identify specific components of the spots by applying a molecular probe (such as a complementary nucleic acid or a radio labeled antibody) — compare southern blot, western blot
: to spot, stain, or spatter with a discoloring substance
: to stain with infamy
: a lone backgammon man exposed to capture
: a weak or exposed point
: a book formerly used in teaching penmanship and containing models for imitation
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