Bounded/unbounded is one of the hypothesized typological parameters that define stress systems (cf. Hayes, 1981).
It fixes the number of syllables of a foot as either two (bounded) or indefinite (unbounded or n-ary).
Hayes, B. 1981. A metrical theory of stress rules. PhD diss. MIT Cambridge, MA. Revised version distributed by IULC, published by Garland Press, New York, 1985.