noun
spent grounds; used tea leaves; used coffee grounds
Refers to tea leaves, coffee grounds, or kelp/bonito flakes after brewing, when the flavor has been extracted.
急須の出し殻を捨ててください。
Please throw away the used tea leaves from the teapot.
コーヒーの出し殻は肥料として使える。
Used coffee grounds can be used as fertilizer.
茶殻 specifically refers to used tea leaves, while 出し殻 can refer to any spent brewing ingredient (tea, coffee, dashi).
Compound of 出し (dashi, 'broth, extraction') and 殻 (kara, 'husk, shell'), with rendaku voicing to gara. Literally 'extraction husk'.