1. [n]  goods or money obtained illegally
2. [n]  (informal) valuable goods
3. [v]  sway heavily or unsteadily
4. [v]  walk as if unable to control one's movements
5. [v]  droop, sink, or settle from or as if from pressure or loss of tautness

1. \Swag\, v. i.
   To tramp carrying a swag. [Australia]
   

2. \Swag\, n. [Australia]
   (a) A tramping bushman's luggage, rolled up either in canvas
       or in a blanket so as to form a long bundle, and carried
       on the back or over the shoulder; -- called also a
       {bluey}, or a {drum}.
   (b) Any bundle of luggage similarly rolled up; hence, luggage
       in general.
             He tramped for years till the swag he bore seemed
             part of himself.                     --Lawson.
   

3. \Swag\, v. i. [imp. & p. p. {Swagged}; p. pr. & vb. n.
   {Swagging}.] [Cf. Icel. sveggja, sveigja to bend, to sway,
   Norw. svaga to sway. See {Sway}.]
   1. To hang or move, as something loose and heavy; to sway; to
      swing. [Prov. Eng.]
   2. To sink down by its weight; to sag. --Sir H. Wotton.
            I swag as a fat person's belly swaggeth as he goeth.
                                                  --Palsgrave.
   

4. \Swag\, n.
   1. A swaying, irregular motion.
   2. A burglar's or thief's booty; boodle. [Cant or Slang]
      --Charles Reade.
   

Scientific (or Silly) Wild Ass Guess. A term used by technical teams when establishing high level sizings for large projects.