recently, i read book. 'charlottes web.'

but i can't understand this sentence exactly.

this sentence.

 ' Charlotte gave her web a twitch and moodily watched it sway.'

i thought about this sentence , structure, words means...

and, changing,

 Charlotte used her web like twitch, and she moodily watched it(web right?) to sway.

Is it same?

actually, i can't completely get word 'twitch' ..

so  i search in my dictionary, it meant ,

   verb, ;1. if a part of your body twiches, or if you twitch it, it makes a sudden quick movement,

             sometimes one that you cannot control

            2. [also VN]

               to give sth a short sharp pull ; to be pulled in this way

       noun ; 1 a sudden quick movement that you cannot control in one of you muscles

                  2  a sudden quick movement or feeling.

   ---------

  maybe it's mean , noun 2  .right?

because  an article is there    head of word 'twitch ' so,   ' a twitch.'

but, i can't understand clearly, how ?

I try to study english everyday, from movie, site, book..

thanks  for read.