Patter

Stability in language is synonymous with rigor mortis.
                                                      –Ernest Weekley

 Words that are their own antonyms

boot -- to start up (as a computer)
boot -- to disable (a vehicle by attaching a Denver boot)

candescent -- glowing or dazzling from great heat
incandescent -- glowing with intense heat

cleave -- to adhere firmly and closely
cleave -- to split apart

dent -- to make a dent in
indent -- to form a dent in

flammable -- capable of being easily ignited and of burning quickly
inflammable -- flammable

garble -- to sift impurities from
garble -- to introduce errors

let -- to hinder, impede
let -- to permit to enter

oversight -- watchful and responsible care
oversight -- inadvertent omission or error

ravel -- to entangle
ravel -- to disentangle
ravel -- to become unwoven, untwisted, or unwound
unravel -- to disengage or separate the threads of

sanction -- official approval
sanction -- loss of official approval

 scan -- to examine by point-by-point observation
scan -- to glance at hastily

sycophant -- slanderer
sycophant -- self-seeking flatterer

table -- to submit (a bill, policy, etc.) for discussion
table -- to postpone discussion (of a bill, policy, etc.)

unqualified -- not fit
unqualified -- not restricted by reservations (unqualified success)