Dictionary.com
Thesaurus.com

floppy disk vs. hard disk

[flop-ee disk] / ˈflɒp i ˈdɪsk /
Or floppydisk

noun

Computers.
  1. a portable storage medium consisting of a square plastic case containing a thin disk coated with magnetic material that is inserted into a drive to read and write data: popular from the 1970s through the 1990s.

[hahrd disk] / ˈhɑrd ˈdɪsk /

noun

Computers.
  1. a rigid circular platter coated with magnetic material, on which data and programs can be stored.