A bobbin thread is the lower thread wound on a small spool. Wind the bobbin thread.
It meets the top thread under the fabric and loops around it, which is how a lock stitch is made. Running out of bobbin thread halfway along a seam is the commonest interruption in sewing.
1nounbobbin threadThe lower thread wound on a small spool.
“The bobbin thread ran out four inches from the end of the hem.”
bobbin thread is a thread.
Practised in Knitting & Sewing