する verb
いんきょする
隠居してから、祖父は毎朝自宅で瞑想をしています。
Since he retired my grandfather had been meditating in his house every morning.
隠居 is retirement. Make that a verb and you have to retire.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well. Will help to know the word 隠居 as well.