A department of activity; a kind or branch of business or occupation.

An area or branch of business or work; a person's occupation, profession, or trade. Frequently more fully way of business. Cf. phrases 7h(a)(ii)…

slang. A line or plan of business, occupation, adventure, etc.; a (particular) job, ‘line’, or ‘tack’: often in on (a certain) lay.

A branch or variety of a specified activity or interest, as trade, literature, science, etc.; a speciality.

A line of work; a ‘lay’. Obsolete. rare.

Originally: an occupation, a profession. Subsequently usually in extended use: a field or department of activity in which a person has special…

A line of work or business; an area or domain of activity or expertise; (a person's) métier.

transferred. An affair, line of business, etc. colloquial.

one's line of country, one's pursuit, field of interest, area of study, etc. (Frequently in neg. contexts.) Also, line of work.