Trompe-l'œil, often written in English as Trompe l'oeil, is an art technique, primarily used in painting, that uses realistic images to create the effect of a three-dimensional optical illusion. Trompe l'oeil is a French term that literally means to "deceive the eye". Though the term trompe l'oeil appeared in the 19th century, the technique has existed at least since Greek and Roman times and is often used when painting murals.
The correct pronunciation of trompe l'oeil is approximately
trohmp luh-yuh. Keep in mind that this is an approximation as the "œ" sound does not have an English equivalent. In the audio pronunciation, you can hear that the second part, transcribed as
luh-yuh, is pronounced with two rather closed "uh" sounds that are close to sounding like an "eh" sound, and these sounds are the key to pronouncing "l'oeil" right. It is fundamental to avoid pronouncing l'oeil as "Loy" because, even if it is quite frequently heard by English speakers, as it is very distant from the correct French pronunciation.