What is the meaning of the word "profess"?

Definitions:

confess one's faith in, or allegiance to verb
- The terrorists professed allegiance to their country
practice as a profession, teach, or claim to be knowledgeable about verb
- They profess organic chemistry.
state freely verb
- I professed to my students that I am not generous when it comes to giving good grades.
state insincerely verb
- They professed innocence but later admitted their guilt.
take vows, as in religious order verb
- I professed myself as a nun.