A Kansai-region abbreviation for McDonald's (the fast-food chain). In other regions people often say 'Makku' or 'Mac'.
昼休み、マクドでハンバーガー買ってくるわ。
I'll go buy a hamburger at McDonald's during lunch break.
関西では『マクド』、関東では『マック』と言う人が多い。
In Kansai people often say 'Makudo,' while in Kanto many say 'Makku' or 'Mac.'
駅前のマクドは24時間営業になったらしい。
I heard the McDonald's in front of the station became 24‑hour.