A "mysterious woman" refers to a woman who is difficult to understand or figure out, often keeping her thoughts, feelings, or intentions hidden or unknown. Full definition
The gorgeous, mysterious woman who keeps crossing his path looks like the perfect distraction from the stress of his new role. (dailyfreebooks.com)
Evan (a tremendous Lou Taylor Pucci) loses his mother to a wasting illness in the same week he loses his job, so he packs it up and goes to Italy, where he encounters a beautiful, mysterious woman named Louise (Nadia Hilker) who happens to have an accent he can't place. (filmfreakcentral.net)
Terrified of real closeness, Frank feels compelled to turn and run, yet he is drawn to this strangely still, mysterious woman with eyes as black as vinyl. (bookbrowse.com)