short back and sides
noun/ˌʃɔːt ˌbæk ən ˈsaɪdz/
/ˌʃɔːrt ˌbæk ən ˈsaɪdz/
[singular] (British English, old-fashioned)- a way of cutting a man’s hair so that the hair is very short at the sides and the back of the head
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short back and sides