countertransport noun 1verb 1forms 3 noun1 •The transport of two chemical species across a membrane in opposite directionsIncreased Na+/Li+ countertransport activity has been described in a study of parents of proteinuric type 1 diabetic patients, although not in another. — 2002 verb1 •To transport two chemical species across a membrane in opposite directions formscountertransported · countertransporting · countertransports