Lady Macbeth's soliloquy is basically her wishing for her femininity to be taken away and replaced with the ruthlessness that only a man could possess at the time. She wants to be 'unsexed', which means that she longer wants to be entailed to the traits of being a female: kind, gentle and nurturing.
It means that her character is ruthless. She's probably the most unconventional female character Shakespeare has ever written. She's manipulative of Macbeth, and demands obedience from him (which at the time, was supposed to be the other way around. Women were viewed as less than men).