Today's (edited, with more) words

éminence grise \ay-mee-nahnss-GREEZ\ - 1. a confidential agent; especially : one exercising unsuspected or unofficial power  2. a respected authority; specifically : an elder statesman

An interesting etymology explains how this phrase has come to have such disparate meaning. 

phalanx \FAY-lanks\ - 1. a body of heavily armed infantry in ancient Greece formed in close deep ranks and files; broadly : a body of troops in close array  2. one of the digital bones of the hand or foot of a vertebrate 3a. a massed arrangement of persons, animals, or things   b. an organized body of persons

Somewhere along the line I apparently learned the correct pronunciation of this word.  When some friends and I stumbled across it in high school - I learned the first definition in the context of a creative writing project when I was searching for an analogy to use for a rook in chess - we mispronounced it as \fuh-LANKS\.  Perhaps I picked up the correct pronunciation along with the second definition, in a graduate-level anatomy and physiology class. 

(Subsequently adding these two from today's Dictionary Devil:)

phonon \FOH-nahn\ - aquantum of vibrational energy (as in a crystal)

I'd never heard of this one at all.

gnomon \NOH-muhn, -mahn\ - 1. an object that by the position or length of its shadow serves as an indicator especially of the hour of the day: as

a. the pin of a sundial
b. a column or shaft erected perpendicular to the horizon  

 2. the remainder of a parallelogram after the removal of a similar parallelogram containing one of its corners

I might have heard of the 1a. definition of this one, but definitely not the rest.