To curse or 'cuss'. Swears are considered inappropriate to use in public places, but are less offensive than other profanities. These 'bad words' are often referenced by pre-adolescents by their first letter (the 'f' word, the 's' word, even 'h-e-double-hockey-sticks').
I swore in the privacy of my room, and nobody was offended.
A very serious and legally binding pact between two or more parties in which blood from each party is placed onto the bottom of the pact next to the signature of each of the parties involved. Amendments to the pact cannot happen without the presence of all former parties present.