Has the opposite meaning to workaholic; someone who habitually works.
A shirkaholic may intentionally or unintentionally never get round to doing any work, filling their day with chit chats, coffee breaks and possibly, internet based distractions
Cedric was a complete shirkaholic, he came in to work at 9:30am then had coffee for half an hour with some cereal. At 10am he would greet his coworkers and then rearrange his desk. He had lunch at midday untill one. Since he didn't smoke, Cedric then checked his emails and replied as nessecary. 3pm brought with it another coffee break and then another tour of the office. He would always go home at 4:30pm to collect a friends' child from after school activites.