mangetout
Concise Oxford English Dictionary © 2008 Oxford University Press:
mangetout /ˈmɒ̃ʒtuː, -ˈtuː/
▶noun (pl. same or mangetouts pronunc. same) Brit. a pea of a variety with an edible pod, eaten when the pod is young and flat.
– origin C19: from Fr., lit. ‘eat all’.
'mangetout' also found in these Oxford entries:

