Plack"et (?), n. [F. plaquer to lay or clap on. See Placard.]
1.
A petticoat, esp. an under petticoat; hence, a cant term for a woman.
[Obs.]
Beau. & Fl.
2.
The opening or slit left in a petticoat or skirt for convenience in putting it on; -- called also placket hole.
3.
A woman's pocket.
© Webster 1913.