Ichidan verb, Transitive verb
to dam up; to hold back; to keep back; to bring to a halt; to intercept
川の水をせき止めるために堤防が建設された。A bank was built to keep back the water of the river. to stem (an activity); to check (e.g. progress)
Also written 堰き止める【せきとめる】、塞き止める【せきとめる】