to 'freak out' means to become overly excited/agitated/upset. to 'flip out' is the same as 'freak out'. Both are commonly used without the word 'out', and mean the same. For example, all these sentences have the same meaning: When my dad sees my grades, he's going to freak out. When my dad sees my grades, he's going to flip out. When my dad sees my grades, he's going to freak. When my dad sees my grades, he's going to flip. When my dad sees my grades, he's going to flip his lid. **** See? They all mean the same thing, and it can be negative or positive, depending on the situation. Hope this helps! :)

Examples of freaked out "Oh my god, I just seen a spider and I totally freaked out." In this usage it means to be startled or scared "There is someone following me I'm about to freak out and start running!" Same thing they're about to show emotions because they feel scared or startled. I would think freaking out could be screaming, crying, or any sort of emotional physical release that is at least semi severe.

http://idioms.thefreedictionary.com/freak+out

If look at this world as verb then freak out - lose one's nerve. For example, when he saw the accident, he freaked out.

freak out = to become upset