"define a "small stock" in terms of volume?"
if it does over 1mill shares, it is not a small stock, although if it trades at $2 a share, obviously a million shares is not a lot
some of my favorite past trading stocks were:
FFIV
HANS (before it became as well known. i also bot it at $10 split adjusted and held it as an investment. my best investment ever, but i traded it in my trading account, while holding it in my investment account)
VPHM
etc.
when you are trading, you are not trading stocks, you are trading other traders. that is distinctly different from INVEStING, where you are investing in the underlying company via the stock.
you want a decent average range, enough liquidity, and there you go