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.

by alongside; in the course of; according to; in relation to; marking the means or instrument (ult. superseding from, through, of) OE.; marking the agent (ult. superseding of, from) XIV. OE. bī, unstressed bi, be = OS., OHG. bī (Du. bij, G. bei), Goth. bi :- Gmc. *bi, prob. identical with the second syll. of Gr. amphi, L. ambi- (see AMBI-, AMPHI-), OE. ymb(e)- around. Cf. BE-, BEFORE, BEHIND, BESIDE, BETIMES, BY-, BY-AND-BY.