'by design' definitions:

Definition of 'by design'

(from WordNet)
adverb
With intention; in an intentional manner; "he used that word intentionally"; "I did this by choice" [syn: intentionally, deliberately, designedly, on purpose, purposely, advisedly, by choice, by design] [ant: accidentally, by chance, circumstantially, unexpectedly, unintentionally]

Synonyms of 'by design'

From: Moby Thesaurus