unbeknownst /ˌʌnbɪˈnoʊnst/ adjective or unbeknown /ˌʌnbɪˈnoʊn/ or unbeknown /ˌʌnbɪˈnoʊn/ Learner's definition of UNBEKNOWNST
unbeknownst/unbeknown to
: without being known about by (someone)不为（某人）所知的；瞒着（某人）的 ◊ In U.S. English unbeknownst is more common than unbeknown. In British English, unbeknown is more common.在美国英语中，unbeknownst比unbeknown更常用。在英国英语中，unbeknown更常用。