To add to the examples and clarify further... Angry and pissed off are both adjectives (strong negative feelings) and have a high intensity level. Irritated and annoyed are either adjectives (milder negative feelings more like something is bothersome rather than a big deal) or past tense verbs speaking about something or someone that brought this feeling about. Freak out is phrasal verb only and suggests that not only was a person very angry but they openly expressed it in a very strong way. Cheers ^^

"Angry" is: Having a strong feeling of or showing annoyance, or displeasure. (Mad) ex: Ellie got angry when she saw her best friend kiss the boy she loved. *" Irritated" is: Making (someone) annoyed, impatient, or angry. ex: Tom always irritated the teacher with his unnecessary, and idiotic, questions. "Freak out" is: lose one's nerve; ex: When he saw the accident, he freaked out. ex2: I freaked out when I saw my favorite band in concert. ex3: The girl freaked out when she saw the table move by itself in the movie. "Annoyed" is: tio irritate (someone); make (someone) a little angry. ex: The rock music was so loud it annoyed the 80 year old neighboors. "Pissed off" is: Like annoyed. Aroused impatience or anger. To become angry. ex: A lot of people were pissed off that the concert was canceled on such short notice. I hope this has somewhat helped you see the difference in the words. :)