A Tac-shi or "Tactical-Shit" is a bowel movement taken preemptively before carrying out any prolonged activity in which there may be very little time ( or no time at all ) to stop and empty one's colon.
Hold up Martin, I've just gotta take a Tac-shi before we hit up another round of Arc Raiders, brb...
an alcoholic beverage mixed by someone whose had way too much to drink. this beverage often contains Captain Morgan, Smirnoff, chocolate milk, tequila, etc. it's a gross mixture, i wouldn't recommend it.
"Andy just made up one of his favorite drinks, called captain on the shi." or "I'm duckin' frunk! Another captain on the shi for me!"