What is the exact definition of a Zonah?
Rashi: A Zonah is a woman who has relations with a Yisrael to whom she is forbidden. 1
R. Akiva (Yevamos 61b): A Zonah is literally a prostitute. 2
R. Eliezer (Yevamos 61b): She is one who had Bi'as Zenus (outside of Kidushin).
Chachamim (Yevamos 61b): She is a convert, freed slave, or one who had Bi'ah with someone forbidden to her. 3
R. Masya ben Charash (Yevamos 61b): Even if a Sotah had Bi'ah with her husband before drinking the water, she became a Zonah.
Rashi: Such as Chayvei Kerisos, a Nasin or a Mamzer.
Rashi (61b): She strays (she is open to have Bi'ah with any man - PF). Also Targum Onkelos and Targum Yonasan translate it like this.
Rashi (Yevamos 15b): I.e. Chayavei Kerisus, or Chayavei Lavim of a Zar me'Ikara (she was forbidden to him from birth, but not Yevamah l'Shuk or Machzir Gerushaso). Ritva (Yevamos 70a) - a Isur to all of Yisrael, e.g. a Petzu'a Daka, even if he is not about Zar me'Ikara.
What is the exact definition of a Chalalah?
Rashi : A Chalalah is the daughter of Pesulei Kehunah 1 (and the woman herself after she has had relations with someone Pasul to Kehunah).
Rashi: A divorcee, a Chalutzah (makes a Chalalah mid'Rabanan) with a Kohen Hedyot, or a widow with a Kohen Gadol. See also Rashbam.
What are the implications of the phrase "Ki Kadosh hu l'Elokav"?
Seforno: All the offspring of a Kohen - who is termed "Ba'al be'Amav" - is sanctified to his G-d. Consequently, in the event that he marries one of these women, he desecrates, not only his own honor, but also his children, who will not be worthy of that Kedushah.
Why does the Pasuk repeat the Inyan of Kedushah so many times in the current Parshah (See Pasuk 6, 7, 8, 15)?
Why does it say "Gerushah me'Ishah"?
Moshav Zekenim (from Toras Kohanim): If a Kohen went overseas, and witnesses [mistakenly] told his wife that he died, and another man was Mekadesh her, and her husband returned, she is permitted to Kehunah even if the latter divorced her, for she was not divorced from Ishah (her true husband).
Moshav Zekenim (from Gitin 82b): If a man divorced her and said 'you are divorced from me, but not permitted to other men', she is disqualified from Kehunah, even after her husband dies, even though she was divorced only from her husband (and not permitted to others). This is called Rei'ach ha'Get, which disqualifies to Kehunah mid'Rabanan.