• an architectural partition with a height and length greater than its thickness; used to divide or enclose an area or to support another structure ...
• anything that suggests a wall in structure or function or effect; "a wall of water"; "a wall of smoke"; "a wall of prejudice"; "negotiations ran into a brick wall"
• (anatomy) a layer (a lining or membrane) that encloses a structure; "stomach walls"
• a difficult or awkward situation; "his back was to the wall"; "competition was pushing them to the wall"
• a vertical (or almost vertical) smooth rock face (as of a cave or mountain)
• a layer of material that encloses space; "the walls of the cylinder were perforated"; "the container's walls were blue"
• a masonry fence (as around an estate or garden); "the wall followed the road"; "he ducked behind the garden wall and waited"
• rampart: an embankment built around a space for defensive purposes; "they stormed the ramparts of the city"; "they blew the trumpet and the walls came tumbling down"
• surround with a wall in order to fortify
  (From Word Search Net)

Boundary walls include privacy walls, boundary-marking walls on property, and city walls. These intergrade into fences; the conventional differentiation is that a fence is of minimal thickness and often is open in nature, while a wall is usually more than a nominal thickness and is completely closed, or opaque. More to the point, if an exterior structure is made of wood or wire, it is generally referred to as a fence, while if it is made of masonry, it is considered a wall. A common term for both is barrier, convenient if it is partly a wall and partly a fence, for example the Berlin Wall. Another kind of wall/fence ambiguity is the ha-ha which is set below ground level, so as not to interrupt a view yet acting as a barrier to cattle for example. (from Wikipedia)

Etymology of wall
O.E. weall "rampart" (natural as well as man-made), also "defensive fortification around a city, side of a building, interior partition," an Anglo-Frisian and Saxon borrowing (cf. O.S., O.Fris., M.L.G., M.Du. wal) from L. vallum "wall, rampart, row or line of stakes," apparently a collective form of vallus "stake." Swed. vall, Dan. val are from Low Ger. In this case, Eng. uses one word where many languages have two, e.g. Ger. Mauer "outer wall of a town, fortress, etc.," used also in ref. to the former Berlin Wall, and wand "partition wall within a building" (cf. the distinction, not always rigorously kept, in It. muro/parete, Ir. mur/fraig, Lith. muras/siena, etc.). The verb meaning "to enclose in a wall" is late O.E. weallian. (Online Etymological Dictionary)

Etymology of fence
c.1330, shortening of defens. Spelling alternated between -c- and -s- in M.E. Sense of "enclosure" is first recorded 1512. Fencible (c.1325) means "capable of making a defense." Sense of "dealer in stolen goods" is thieves' slang, first attested c.1700, from notion of such transactions taking place under defense of secrecy. To be figuratively on the fence "uncommitted" is from 1828, from the notion of spectators at a fight. (Online Etymological Dictionary)

Etymology of border
c.1350, from O.Fr. bordure "seam, edge, border," from Frankish bord (cf. O.E. bord "side"), from P.Gmc. bordus "edge," from borthaz. The geopolitical sense first attested 1535, in Scottish (replacing earlier march), from The Borders, district adjoining the boundary between England and Scotland. (Online Etymological Dictionary)

Etymology of march (obs.) "boundary," c.1290 (in ref. to the borderlands beside Wales, rendering O.E. Mercia), from O.Fr. marche "boundary, frontier," from Frank. marka (cf. O.H.G. marchon "to mark out, delimit," Ger. Mark "boundary." (Online Etymological Dictionary)

Etymology of pale
c.1330, "fence of pointed stakes," from L. palus "stake," related to pangere "to fix or fasten." Fig. sense of "limit, boundary, restriction" is from c.1400. Barely surviving in beyond the pale and similar phrases. Meaning "the part of Ireland under English rule" is from 1547. (Online Etymological Dictionary)

Etymology of limbo
"region supposed to exist on the border of Hell" reserved for pre-Christian saints (Limbus patrum) and unbaptized infants (Limbus infantum);" c.1300, from L. (in) limbo "(on) the edge," abl. of limbus "edge, border." Figurative sense of "condition of neglect or oblivion" is from 1642. (Online Etymological Dictionary)