by / bī/ • prep. 1. identifying the agent performing an action: ∎ after a passive verb: the door was opened by my cousin Annie. ∎ after a noun denoting an action: further attacks by the mob a clear decision by the electorate. ∎ identifying the author of a text, idea, or work of art: a book by Ernest Hemingway.2. indicating the means of achieving something: malaria can be controlled by attacking the parasite. ∎ indicating a term to which an interpretation is to be assigned: what is meant by “fair?” ∎ indicating a name according to which a person is known: she mostly calls me by my last name. ∎ indicating the means of transport selected for a journey: traveling by train to Boston. ∎ indicating the other parent of someone's child or children: Richard is his son by his third wife. ∎ indicating the sire of a pedigree animal, esp. a horse: a black filly by Goldfuerst. ∎ (followed by a noun without an adjective) in various phrases indicating how something happens: I heard by chance that she has married again.3. indicating the amount or size of a margin: the shot missed her by miles. ∎ indicating a unit of measurement: billing is by the minute. ∎ in phrases indicating something happening repeatedly or progressively, typically with repetition of a unit of time: colors changing minute by minute. ∎ identifying a parameter: a breakdown of employment figures by age and occupation. ∎ expressing multiplication, often in dimensions: a map measuring 24 by 36 inches she multiplied it by 89.4. indicating a deadline or the end of a particular time period: I've got to do this report by Monday.5. indicating location of a physical object beside a place or object: remains were discovered by the roadside. ∎ past; beyond: I drove by our house.6. indicating the period in which something happens: this animal always hunts by night.7. concerning; according to: anything you do is all right by me she had done her duty by him.8. used in mild oaths: it was the least he could do, by God.• adv. so as to go past: a car flashed by on the other side of the road he let only a moment go by.• n. (pl. byes) variant spelling of bye1 .PHRASES: by and by before long; eventually.by the by (or bye) incidentally; parenthetically: where's Hector, by the by?by and large on the whole; everything considered: mammals have, by and large, bigger brains than reptiles.by oneself1. alone: living in that big house by himself.2. unaided: the patient often learns to undress by himself.