also: もくし
noun
mottled yarn; mock twist yarn
A type of yarn with a variegated or speckled appearance, used in textiles. The English terms 'grandrelle yarn', 'mouline yarn', 'mottled yarn', and 'mock twist yarn' all refer to similar or overlapping concepts.
このセーターは杢糸で編まれている。
This sweater is knitted with mottled yarn.
杢 (moku, 'wood grain' or 'mottled pattern') + 糸 (ito, 'thread'). The reading もくし is a contraction of もくいと.