The way a person conducts his life, whether good or bad.
المعنى الاصطلاحي :
Rules that regulate the interactions between the Muslims and others in peace and war based on the conduct and way of the Prophet, may Allah’s peace and blessings be upon him, in dealing with his enemies.
الشرح المختصر :
"Seerah" (rules of engagement) is the system of rules set by the Prophet, may Allah’s peace and blessings be upon him, for the ruler to follow with his conquering soldiers when fighting the infidels, and with all others. This includes how he deals with the following groups: the members of his army; the enemy soldiers; non-believers including those who are at war with Muslims; those who have a pact with Muslims; apostates; rebels against the Muslim state; and so on, as related in the Prophet’s manner of interactions, may Allah’s peace and blessings be upon him. Military expeditions were called "siyar" (paths or ways), because their initial stage is treading a path towards the enemy. In modern terms, this is called international law.
التعريف اللغوي المختصر :
"Seerah" (pl. "siyar"): way of conduct, whether good or bad. Derived from "sayr", which means continuing, flowing. A person is said to have a good "seerah" among people if he demonstrates good conduct and manners in dealing with them.