burden

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

• noun Something that is carried.
• noun Something that is emotionally difficult to bear.
• noun A source of great worry or stress; weight.
• noun A responsibility or duty.
• noun A principal or recurring idea; a theme.
• noun A drone, as of a bagpipe or pedal point.
• noun Archaic The chorus or refrain of a composition.
• noun Archaic The bass accompaniment to a song.
• noun The amount of cargo that a vessel can carry.
• noun The weight of the cargo carried by a vessel at one time.
• noun The amount of a disease-causing entity present in an organism.
• transitive verb To cause difficulty or distress to; distress or oppress.
• transitive verb To load or overload.

from The Century Dictionary.

• noun The act of bearing children; a birth.
• noun That which is borne or carried; a load.
• noun Hence That which is borne with labor or difficulty; that which is grievous, wearisome, or oppressive; also, an incumbrance of any kind.
• noun In England, a quantity of certain commodities: as, a burden of gad-steel (that is, 120 or 180 pounds).
• noun The capacity of a ship; the quantity or number of tons of freight a vessel will carry: as, a ship of 600 tons burden.
• noun In mining, the tops or heads of stream-work, overlying the stream of tin, and needing to be first cleansed.
• noun The charge of a blast-furnace.
• noun The bass in music.
• noun In music: The refrain or recurring chorus at the end of the stanzas of a ballad or song; a refrain.
• noun The drone of a bagpipe. The song to which a dance is danced when there are no instruments.
• noun That which is often repeated; a subject on which one dwells; the main topic: as, this subject was the burden of all his talk.
• To load; lay a heavy load on; encumber with weight.
• Hence Figuratively, to load; oppress with anything which is borne with difficulty or trouble; surcharge: as, to burden a nation with taxes; to burden the memory with details.
• To lay or impose upon one, as a load, burden, or charge.
• noun A club.

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

• noun obsolete A club.
• noun That which is borne or carried; a load.
• noun That which is borne with labor or difficulty; that which is grievous, wearisome, or oppressive.
• noun The capacity of a vessel, or the weight of cargo that she will carry.
• noun (Mining) The tops or heads of stream-work which lie over the stream of tin.
• noun (Metal.) The proportion of ore and flux to fuel, in the charge of a blast furnace.
• noun A fixed quantity of certain commodities.
• noun Obs. & R. A birth.
• noun an animal employed in carrying burdens.
• noun (Law) the duty of proving a particular position in a court of law, a failure in the performance of which duty calls for judgment against the party on whom the duty is imposed.
• transitive verb To encumber with weight (literal or figurative); to lay a heavy load upon; to load.
• transitive verb To oppress with anything grievous or trying; to overload.
• transitive verb rare To impose, as a load or burden; to lay or place as a burden (something heavy or objectionable).
• noun The verse repeated in a song, or the return of the theme at the end of each stanza; the chorus; refrain. Hence: That which is often repeated or which is dwelt upon; the main topic.
• noun The drone of a bagpipe.

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

• noun obsolete A club (weapon).
• noun A heavy load.
• noun A responsibility, onus.
• noun A cause of worry.