[adjective] [not gradable] [slightly formal] - tantamount to being almost the same or having the same effect as (usually something bad)The bank wouldn't lend any more money, which was tantamount to making the business close down.Her refusal to answer was tantamount to an admission of guilt.
TANTAMOUNT
Meaning of TANTAMOUNT in English
Cambridge English vocab. Кембриджский английский словарь. 2012