A geometric optical aberration that causes straight lines in the object space to appear curved in the image. It occurs when the magnification of a lens is not constant across its entire field. The two most common forms are barrel distortion, where magnification decreases toward the edges, and pincushion distortion, where magnification increases toward the edges.
Heard on the job
We need to correct the barrel distortion in post because the wide-angle lens warped the architectural lines.