unthinking

US /ʌnˈθɪŋ.kɪŋ/
UK /ʌnˈθɪŋ.kɪŋ/
1.

không suy nghĩ

not based on serious thought or an examination of the information:

:
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What annoys me about these people is their unthinking hostility to anything foreign or unfamiliar.