1. A manufactured fiber that is essentially a physical combination or mixture of two or more chemically distinct constituents or components combined at or prior to the time of extrusion (i.e., produced in fiber form), which components if separately extruded would each fall within different definitions of textile fiber. (FTC definition). Matrix fibril fibers have the fibril constituent randomly arranged across the cross section of the matrix. When the fibril component is in high concentration it may actually form a fibrillar network in the matrix.

2. In aerospace textiles, a thermoplastic fiber used with reinforcing fiber to form a composite after consolidation with heat and pressure.

3. In nonwovens manufacture, fibers that are blended with low-melt fibers to form a thermally bonded fabric.