吐丝 literally means 'to expel silk' — combining 吐 (tǔ, 'to spit out, eject') and 丝 (sī, 'silk, thread'). It describes the biological process by which silkworms secrete liquid silk protein from their salivary glands and draw it into fine, continuous filaments as they form cocoons. This is a defining behavior of the silkworm (Bombyx mori) during its pupal stage.

Beyond its literal entomological meaning, 吐丝 is also used figuratively in modern Chinese to describe the gradual, deliberate production of ideas, insights, or creative output — much like how a silkworm slowly spins its silk. This metaphor emphasizes patience, continuity, and organic development, often appearing in academic, literary, or artistic contexts. While the literal sense is concrete and zoological, the figurative use is idiomatic and slightly literary, conveying quiet, sustained effort rather than sudden inspiration.