Which makeup product is typically used to define the eyebrows?

Brow gel is specifically designed to define and shape eyebrows, making it the ideal product for this purpose. It can add color, hold hairs in place, and create a more polished look, enhancing the natural shape of the eyebrows. Unlike other products, brow gel is formulated to adhere to brow hairs without feeling heavy or greasy, often providing a more natural finish.

Eyeliner is designed for enhancing the eyes and does not offer the same texture or hold that brow products do. Concealer is primarily used to cover imperfections on the skin, particularly under the eyes and on blemishes, rather than to define hair. Foundation is meant for evening out skin tone and does not have the properties necessary for shaping or defining brow hairs. Thus, brow gel stands out as the best option for defining eyebrows effectively.