What is "to protest a bill"

Protest \Pro*test"\, v. t.

1. To make a solemn declaration or affirmation of; to proclaim; to display; as, to protest one's loyalty.

   I will protest your cowardice.
   --Shak.

2. To call as a witness in affirming or denying, or to prove an affirmation; to appeal to.

   Fiercely [they] opposed My journey strange, with clamorous uproar Protesting fate supreme.
   --Milton.

   To protest a bill or To protest a note (Law), to make a solemn written declaration, in due form, on behalf of the holder, against all parties liable for any loss or damage to be sustained by the nonacceptance or the nonpayment of the bill or note, as the case may be. This should be made by a notary public, whose seal it is the usual practice to affix.
   --Kent.
   --Story.