1) Large crude carrier 2) Large oil transporter 3) Oil tanker 4) Oiler 5) Tank ship 6) Tanker 
large tanker (q.v.) or cargo ship, commonly an oil-carrying vessel that might exceed 500,000 tons deadweight.[2 related articles]
[n] - the largest class of oil tankers
supertanker A very large, above normal, oil tanker; typically defined as a vessel designed to transport more than 500,000 dead-weight tons of oil.
noun the largest class of oil tankers
a tanker with a deadweight capacity of over 75,000 tons.