What does "glean" mean?

Additional senses

1. 2.To collect with patient and minute labor; to pick out; to obtain. Content to glean what we can from . . . experiments. Locke.
2. 3.To gather stalks or ears of grain left by reapers. And she went, and came, and gleaned in the field after the reapers. Ruth ii.
3. 4.2. To pick up or gather anything by degrees. Piecemeal they this acre first, then that; Glean on, and gather up the whole estate. Pope.
4. 5.A collection made by gleaning. The gleans of yellow thyme distend his thighs. Dryden.
5. 6.Cleaning; afterbirth. [Obs.] Holland.