I was in the garden covered with mud when my grandmother dropped in for a visit.
Most beginners are blissfully unaware that dropping in on someone is a cardinal sin — Neal Miyake, The Unwritten Rules of Surfing.
The office was efficient, but not well equipped to handle drop-ins.
2005: Drop-ins can and do happen by accident, as well as through frustration and confusion in a crowded lineup. — surfline.com Surfology.