marginal

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Of, relating to, located at, or constituting a margin, a border, or an edge.
• adjective Being adjacent geographically.
• adjective Written or printed in the margin of a book.
• adjective Barely within a lower standard or limit of quality.
• adjective Having to do with enterprises that produce goods or are capable of producing goods at a rate that barely covers production costs.
• adjective Relating to commodities thus manufactured and sold.
• adjective Psychology Relating to or located at the fringe of consciousness.
• noun One that is considered to be at a lower or outer limit, as of social acceptability.

from The Century Dictionary.

• Pertaining to a margin; situated on or near the margin; specifically, written or printed in the margin of a page: as, a marginal note or gloss.
• noun One of the bones which form the border of the carapace in turtles, except in the Trionychoidea, in which they are lacking: same as marginal plate. See cut under carapace, 1.
• noun In the ammonoid cephalopods, or ammonites, one of the small inflections which sometimes develop on the sides of the antisiphonal lobe of the sutures.
• noun In conchology, one of the outermost teeth on the radula of gastropods; one of the uncini.
• noun In asteroid echinoderms, one of the series of thick plates round the margin of the arms and disk.

from the GNU version of the Collaborative International Dictionary of English.

• adjective Of or pertaining to a margin.
• adjective Written or printed in the margin.
• adjective At the lower limit; barely sufficient.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective not comparable Of, relating to, or located at or near a margin or edge; also figurative usages of location and margin (edge).
• adjective comparable Determined by a small margin; having a salient characteristic determined by a small margin.
• noun Something that is marginal.
• noun A constituency won with a small margin.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective of questionable or minimal quality
• adjective at or constituting a border or edge
• adjective just barely adequate or within a lower limit
• adjective producing at a rate that barely covers production costs