Used as swear word (common in french Canadian slang) 'Tabarnak' has a variety of uses. It has nearly become an equivalent to "fuck" and its derivatives in how it is used. It can be used as an insult (when adressing someone),or to overstate/amplify an emotion/state of mind, or to express surprise-disgust, etc.
Mon/le -tabarnak- (in keeping with the fuck reference: you/that -fucker-) ~insult~
C'est beau en -tabarnak- (It's -fucking- pretty) ~to amplify, overstate~
tabarnak! (fuck!) ~to express surprise in response to a comment, for example~