WordNet
damping off
n. a plant disease caused by a fungus; diseased condition of seedlings in excessive moisture
Wikipedia
Damping off
Damping off (or damping-off) is a horticultural disease or condition, caused by a number of different pathogens that kill or weaken seeds or seedlings before or after they germinate. It is most prevalent in wet and cool conditions.
Usage examples of "damping off".
Keep the seedlings in their seed-boxes, freely ventilated to prevent damping off, and in April remove them to a sheltered shady border.