under lock and key

:  in or into a position below or beneath something

:  below or short of some quantity, level, or limit

:  in or into a condition of subjection, subordination, or unconsciousness

:  below or beneath so as to be overhung, surmounted, covered, protected, or concealed by

:  subject to the authority, control, guidance, or instruction of

:  receiving or undergoing the action or effect of

:  lower in rank or authority :  subordinate

:  a tuft, tress, or ringlet of hair

:  the hair of the head

:  a cohering bunch (as of wool, cotton, or flax) :  tuft

:  a fastening (as for a door) operated by a key or a combination

:  the mechanism for exploding the charge or cartridge of a firearm

:  an enclosure (as in a canal) with gates at each end used in raising or lowering boats as they pass from level to level

:  to fasten the lock of

:  to make fast with or as if with a lock

:  to fasten in or out or to make secure or inaccessible by or as if by means of locks

:  a usually metal instrument by which the bolt of a lock is turned

:  any of various devices having the form or function of such a key

:  a means of gaining or preventing entrance, possession, or control

:  extremely or crucially important

:  to lock or secure with or as if with a key :  fasten: such as

:  to secure (something, as a pulley on a shaft) by a key

:  to finish off (an arch) by inserting a keystone

:  a low island or reef

:  any of the coral islets off the southern coast of Florida

:  a kilogram especially of marijuana or heroin