What is "plaining"

Plaining \Plain"ing\, n. Complaint. [Poetic]
--Shak.

Plaining \Plain"ing\, a. Complaining. [Poetic]
--Bryant.

Plain \Plain\, v. t. [imp. & p. p. Plained; p. pr. & vb. n. Plaining.] [Cf. Plane, v.]

1. To plane or level; to make plain or even on the surface.

   We would rake Europe rather, plain the East.
   --Wither.

2. To make plain or manifest; to explain.

   What's dumb in show, I'll plain in speech.
   --Shak.

n. A lamentation. vb. (present participle of plain English)