A French phrase meaning 'in the style of Nice' ('niçoise' is the feminine form of niçois', meaning 'of Nice'). While there is some uncertainty in American books about what exactly the style of Nice is, it generally means that it includes tomatoes, black olives, garlic, and anchovies. It may also include tuna, hard-boiled eggs, green beans, basil, lemon, and capers.
'A la niçoise' is most often seen in English when referring to salad; it is often shortened to simply salade nicoise. But any number of dishes, both hot and cold can be made à la niçoise, being baked, stuffed, or served with some combination of the above mentioned ingredients.
It is pronounced (roughly) as ah lah nee-swahz