marginal (adj.)

• borderline
• bounding
• coastal
• determinant
• determinative
• determining
• disputable
• doubtful
• dubious
• extreme
• inferior
• infinitesimal
• insignificant
• limbic
• liminal
• limiting
• littoral
• minimal
• negligible
• questionable
• rimming
• secondary
• skirting
• slight
• small
• terminal
• tiny
• unimportant