1
general::
1. Pluck or pull at, especially with the fingers, as in She was always picking at her skirt with her nails. [1600s] 2. Eat sparingly and without appetite, as in He was just picking at his dinner. [Late 1500s] 3. Nag, badger, as in He's picking at me all day long. [Colloquial; second half of 1600s]
American Heritage Idioms
2
general::
Phrase(s): pick at something
1. Lit. to try to pull away bits of something. • Don’t pick at the bookbinding. It will fall apart. 2. Fig. to eat just a tiny bit of a meal or some kind of food. • You are just picking at your food!, Phrase(s): pick at someone or something
to be very critical of someone or something; to pick on someone or something. • Why are you always picking at me? • The critics picked at the little things, missing the serious problems.
McGrawhill's American Idioms And Phrasal Verbs