Synecdoche

syn·ec·do·che

Definition:
1–nounRhetoric.
a figure of speech in which a part is used for the whole or the whole for a part, the specific for the general or the general for the specific, or the material for the thing made from it

Examples -- Referring to the general specifically (big to small, whole to part)

1) Reffering to workers as "hands" as in "all hands on deck"

Examples -- Referring to the specific generally (small to big, part to whole)

1) Referring to police officers as "the law"

2) Using the word cutthroat to mean assassin

3) Using the word thief to mean pickpocket

Examples -- Referring to an object as what it is made of

1) Using the word steel to mean sword