1.
father-in-law
One's spouse's father, or a stepfather. The 義理 prefix indicates a family relationship by marriage rather than blood.
Usage
The 義理の〜 pattern creates in-law family terms: 義理の父 (father-in-law), 義理の母 (mother-in-law), 義理の兄弟 (brother/sister-in-law). When speaking about one's own father-in-law to others, use 義理の父. When addressing him directly, use お義父さん.
Note: 義理 here indicates a relationship by marriage, not by blood.