A person who is obcessed with using periods in Instant Messages. Typically uses improper grammar with the only punctuation being periods. In some cases, the periods come between words, as a comma would.
Periodisiac Example1: "dang. that was awesome. wow."
The slight swelling and sensitivity of the breasts which a woman experiences for a few days, just before having her menstruation.
The word "periodical" refers to both the cause of the increase in size and the short duration.
As opposed to "major boobage", the effect is minor and temporary.
Man: Wow! Your breasts have really gotten bigger! Did you get implants?
Woman: No, they are only periodical boobs. They'll be back to normal in a few days.