Wiktionary
n. A condiment generally made with diced raw onions, tomatoes, chiles, and cilantro.
Wikipedia
In Mexican cuisine, pico de gallo (, literally beak of rooster), also called salsa fresca, is made from chopped tomato, onion, coriander leaves, fresh serranos ( jalapeños or habaneros are used as alternatives), salt, and key lime juice. Other ingredients, such as shrimp or avocado, are also sometimes added.
Pico de gallo can be used in much the same way as other Mexican liquid salsas, but since it contains less liquid, it can also be used as a main ingredient in dishes such as tacos and fajitas.
The tomato-based variety is widely known as salsa picada ( minced/chopped sauce). In Mexico it is sometimes called salsa mexicana (Mexican sauce). Because the colors of the red tomato, white onion, coriander and green chili are reminiscent of the colors of the Mexican flag, it is also sometimes called salsa bandera (flag sauce).
In many regions of Mexico the term refers to any of a variety of salads (including fruit salads), salsa, or fillings made with tomato, tomatillo, avocado, orange, jícama, cucumber, papaya, or mild chilis. The ingredients are tossed in lime juice and either hot sauce or chamoy, then sprinkled with a salty chili powder.