Initialism of Territorial Army.

(countable) Initialism of transportation authority. / (countable) Initialism of teaching assistant. / (countable) Initialism of travel agent. / (countable) Initialism of target audience.

(intransitive) To act as a teaching assistant.

(microbiology) Initialism of toxin-antitoxin.

A small nail with a flat head. / A thumbtack. / (sewing) A loose seam used to temporarily fasten pieces of cloth.

To nail with a tack (small nail with a flat head). / To sew/stitch with a tack (loose seam used to temporarily fasten pieces of cloth).

A stain; a tache. / (obsolete) A peculiar flavour or taint.

(colloquial) That which is tacky; something cheap and gaudy.

(law, Scotland and Northern England) A contract by which the use of a thing is set, or let, for hire; a lease.

(colloquial, chiefly Britain, Ireland, Australia and New Zealand) Thanks. / (Canada, childish) give (imperative)