What is thread? What is thread? Fine cord of a fibrous material, such as cotton or flax, made of two or more filaments twisted together and used in needlework and the weaving of cloth.A piece of such cord.A thin strand, cord, or filament of natural or manufactured material. Something that suggests the fineness or thinness of such a strand, cord, or filament: a thread of smoke. Something that suggests the continuousness of such a strand, cord, or filament: lost the thread of his argument. A helical or spiral ridge on a screw, nut, or bolt.Computer Science A portion of a program that can run independently of and concurrently with other portions of the program.Computer Science A set of posts on a newsgroup, composed of an initial post about a topic and all responses to it.Slang Clothes.To pass one end of a thread through the eye of (a needle, for example).To pass (something) through in the manner of a thread: thread the wire through the opening. To pass a tape or film into or through (a device): thread a film projector. To pass (a tape or film) into or through a device.To connect by running a thread through; string: thread beads. To make one's way cautiously through: threading dark alleys. To make (one's way) cautiously through something.To occur here and there throughout; pervade: "More than 90 geologic faults thread the Los Angeles area” ( Science News). To machine a thread on (a screw, nut, or bolt).To make one's way cautiously: threaded through the shoals and sandbars. To proceed by a winding course.To form a thread when dropped from a spoon, as boiling sugar syrup.