Sig is a commonly used abbreviation for the word "Sigma." In the context of the clue you provided, "Phi ___ (college group, familiarly)," it is likely referring to a fraternity or sorority that uses the Greek letter Phi in their name and is commonly known by the nickname or familiar name "Sig."
Note: The provided meaning of the answer is for the latest New York Times crossword puzzle clue: Phi ___ (college group, familiarly). Explanations are generated by AI and may be inaccurate.