amphipod
Concise Oxford English Dictionary © 2008 Oxford University Press:
amphipod /ˈamfɪpɒd/
▶noun Zoology a crustacean of the chiefly marine order Amphipoda, having a laterally compressed body and a large number of leg-like appendages.
– origin from mod. L. Amphipoda, from amphi- ‘of both kinds’ (because some legs are specialized for swimming and some for feeding) + Gk pous, pod- ‘foot’.
'amphipod' also found in these Oxford entries:

