undrain noun 1verb 1forms 3 noun1 •A water collection system that drains water away from a location.The experiments with fresh and septic sludge show that for filters of the same size material, fresh sludge passes through into the undrains while septic sludge merely gives up its water. — 1911 verb1 •To restore that which has drained away.The probable differences between gross and net drain also require an explanation of why some manpower "undrains" by returning home after a period of working in the United States. — 1970 formsundrained · undraining · undrains
