Clean bomb and Plutonium bomb

Clean bomb noun - An atom bomb leaving little or no radioactive contamination.

Plutonium bomb and clean bomb are semantically related. In some cases you can use "Plutonium bomb" instead a noun phrase "Clean bomb".

Plutonium bomb noun - A nuclear weapon in which enormous energy is released by nuclear fission (splitting the nuclei of a heavy element like uranium 235 or plutonium 239).

Clean bomb and plutonium bomb are semantically related. Sometimes you can replace phrase "Clean bomb" with "Plutonium bomb", this phrases are similar.