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bow down (We shall never bow down to our enemies – Мы никогда не склонимся перед врагом Taras); throw up one's cards; concede; give up (MichaelBurov); admit defect (Till I Die); concede defeat (Kendall conceded defeat once she realized she could not win in a battle of wits. В.И.Макаров); own defeat ("Her courage was admirable. Even now she would not own defeat." – Sir Arthur Conan Doyle ART Vancouver); admit defeat (VLZ_58)

ajedr.

acknowledge defeat

austral., jerg.

throw it in; toss in the towel

fig.

tap out (Andreyka)

idiom.

throw in the towel (4uzhoj)

inf.

take a loss (Баян)

jerg.

pack it in; throw in the sponge (towel); toss it in; toss in the sponge (Interex)