Multitran dictionary

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phrases | Google | Forvo | +
 a big ask
brit., inform. просьба, которую трудно выполнить (or a tough ask // British, Australian and New Zealand informal: a task which is difficult to fulfil; something you ask someone to do that will be difficult for them:: It's a big ask, I know, but we need the project finished by June.)
idiom. трудновыполнимая просьба (akimboesenko)
a big ask: 3 phrases in 3 subjects
American usage, not spelling1