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1.OBDURATE: hardened in feeling , resistant to persuasion

similar meanings: TENACIOUS      INTRANSIGENT         RECALCITRANT  
                               UNYIELDING      

2.OBSEQUIOUS: overly submissive  and  eager to please

similar meanings: COMPLIANT      DEFERENTIAL      SERVILE      SUBSERVIENT

3.OBSTINATE:  stubborn , unyielding

similar meanings: INTRANSIGENT      TENACIOUS      PERTINACIOUS      MULISH

4.OBVIATE: to prevent , to make unnecessary

similar meanings: FORESTALL      PRECLUDE        PROHIBIT

5.OCCLUDE: to stop up , to prevent the passage of

similar meanings: BARRICADE     BLOCK      CLOSE       OBSTRUCT

6.ONEROUS: troublesome and oppressive , burdensome

similar meanings: BACKBREAKING         CUMBERSOME       LABORIOUS       HARD
                              FORMIDABLE                OPPRESSIVE           RIGOROUS
                              TAXING                             TRYING

7.OPAQUE: impossible to see through , preventing the passage of light

similar meanings:  OBSCURE

8.OPPROBRIUM: public disgrace

similar meanings:  DISCREDIT      IGNOMINY       INFAMY        OBLOQUY     SHAME
                               DISHONOR

9.OSTENTATION: excessive showiness

similar meanings: CONSPICUOUSNESS       PRETENTIOUSNESS        FLASHINESS