a phrase used to express an attitude of somebody that is full of energy, vigor, perhaps rowdiness or excitedness.
Dottering Old Man: Well hello there young fella! How might you be feeling today?
Timmy: I'm full of piss and vinegar, you crotchety ol' coot! Now, outta my way, I'm going to play with my friends!
Dottering Old Man: Good to hear! Say, I'll give you a lollipop if you squeeze my testicles two or three times!