impression

noun

1. (countable, uncountable)The indentation or depression made by the pressure of one object on or into another.

   “His head made an impression on the pillow.”

2. (countable, uncountable)The overall effect of something, e.g., on a person.

   “He tried to make a good impression on his parents.”

   “Their empires, triumphs, conquests, and projects, have left little impression behind them, notwithstanding the attention they once attracted, and the violent convulsions which they caused in the state of the world.”

   “The stories did not seem to me to touch life. […] They left me with the impression of a well-delivered stereopticon lecture, with characters about as life-like as the shadows on the screen, and whisking on and off, at the mercy of the operator.”

   “Though most of the cases here cover European encounters with non-Europeans, it is not the intention of the book to give the impression that genocide is a function of European colonialism and imperialism alone.”

3. (countable, uncountable)A vague recalling of an event, a belief.

   “I have the impression that he's already left for Paris.”

4. (countable, uncountable)An impersonation, an imitation of the mannerisms of another individual.
5. (countable, uncountable)An outward appearance.
6. (Internet, countable, uncountable)A performance metric representing an instance where a post or ad is shown once.

   “Publishers are paid for each ad impression their site generates.”

7. (countable, uncountable)The first coat of colour, such as the priming in house-painting etc.
8. (countable, uncountable)A print on paper from a wood block, metal plate, etc.
9. (countable, uncountable)The vivid perception of something as it is experienced, in contrast to ideas or thoughts drawn from memory or the imagination.

   “Let us, therefore, use a little freedom, and call them Impressions; employing that word in a sense somewhat different from the usual. By the term impression, then, I mean all our more lively perceptions, when we hear, or see, or feel, or love, or hate, or desire, or will. And impressions are distinguished from ideas, which are the less lively perceptions, of which we are conscious, when we reflect on any of those sensations or movements above mentioned.”

10. (countable, uncountable)set of copies of a publication printed at one time having the same content, layout, pagination, etc.

verb

1. To manipulate a blank key within a lock so as to mark it with impressions of the shape of the lock, which facilitates creation of a duplicate key.

   “The trick in impressioning a key is to remove only a small amount of the blank, by filing or cutting, from the pin positions where impressions have been left.”