Source : Webster's Revised Unabridged Dictionary (1913)

Marginal \Mar"gin*al\, a. [Cf. F. marginal.]
   1. Of or pertaining to a margin.

   2. Written or printed in the margin; as, a marginal note or
      gloss.

Source : WordNet®

marginal
     adj 1: at or constituting a border or edge; "the marginal strip of
            beach" [syn: {fringy}]
     2: of questionable or minimal quality; "borderline grades";
        "marginal writing ability" [syn: {borderline}]
     3: of a bare living gained by great labor; "the sharecropper's
        hardscrabble life"; "a marginal existence" [syn: {hardscrabble}]
     4: just barely adequate or within a lower limit; "a bare
        majority"; "a marginal victory" [syn: {bare(a)}]
     5: producing at a rate that barely covers production costs;
        "marginal industries"; "marginal land"
     6: of something or someone close to a lower limit or lower
        class; "marginal abilities"

Source : Free On-Line Dictionary of Computing

marginal
     
         1. Extremely small.  "A marginal increase in {core}
        can decrease {GC} time drastically."  In everyday terms, this
        means that it is a lot easier to clean off your desk if you
        have a spare place to put some of the junk while you sort
        through it.
     
        2. Of extremely small merit.  "This proposed new feature seems
        rather marginal to me."
     
        3. Of extremely small probability of {win}ning.  "The power
        supply was rather marginal anyway; no wonder it fried."
     
        [{Jargon File}]
     
        (1994-10-21)