What does "thumb" mean?

Additional senses

1. 2.To play with the thumbs, or with the thumbs and fingers; as, to thumb over a tune.
2. 3.To soil or wear with the thumb or the fingers; to soil, or wear out, by frequent handling; also, to cover with the thumb; as, to thumb the touch-hole of a cannon. He gravely informed the enemy that all his cards had been thumbed to pieces, and begged them to let him have a few more packs. Macaulay.
3. 4.To play with the thumb or thumbs; to play clumsily; to thrum.