What Does "Suck" Means?

Suck means to draw in liquid and especially mother's milk with the mouth,to draw liquid by action to the mouth,to allowto desolve graduallyin the mouth,to put ( as a thumb)into the mouth and drawon as if sucking. Or, the easy way, to absorb

From Websters Dictionary:
1 a: To draw (as liquid) into the mouth through a suction force produced by movements of the lips and tongue  b: To draw something from or consume by such movements   c: To apply the mouth to in order to or as if to suck out a liquid
2 a: To draw by or as if by suction   b: To take in and consume by or as if by suction   
1: To draw something in by or as if by exerting a suction force ; especially : To draw milk from a breast or udder with the mouth
2: To make a sound or motion associated with or caused by suction  
3: To act in an obsequious manner  —usually used with up
4slang : To be objectionable or inadequate

It mean to licks something