In Skyfall, besides describing woman as a challenge, the word also describes the woman as a temptress, an alluring woman who seduces and/or exploits men. So bond pretty much covered everything in a woman, alluring, seductive, challenging, and with a possibility of exploiting her man.

The term you probably heard in Skyfall, in that particular context, Provocatrix means a Challenger, and a Challenger (female) in that context means something or someone challenging. So, Bond described a woman as a "challenge."