Bilinear interpolation
From The Glossary of Digital Photography
A method of creating additional pixels by interpolating from four other pixels. It is not as widely used as bicubic interpolation when enlarging an image. See also bicubic filtering

ONLINE GLOSSARY OF DIGITAL PHOTOGRAPY
A method of creating additional pixels by interpolating from four other pixels. It is not as widely used as bicubic interpolation when enlarging an image. See also bicubic filtering