Noun back up has 5 senses
  1. backup - an accumulation caused by clogging or a stoppage; "a traffic backup on the main street"; "he discovered a backup in the toilet"
    --1 is a kind of accretion, accumulation
    Derived form: verb back up5
  2. stand-in, substitute, relief, reliever, backup, backup man, fill-in - someone who takes the place of another (as when things get dangerous or difficult); "the star had a stand-in for dangerous scenes"; "we need extra employees for summer fill-ins"
    --2 is a kind of peer, equal, match, compeer
    --2 has particulars:
     locum tenens, locum; double, stunt man, stunt woman; surrogate, alternate, replacement
  3. accompaniment, musical accompaniment, backup, support - a subordinate musical part; provides background for more important parts
    --3 is a kind of part, voice
    --3 has particulars: descant, discant; vamp
  4. backup, computer backup - (computer science) a copy of a file or directory on a separate storage device; "he made a backup in case the original was accidentally damaged or erased"
    --4 is a kind of duplicate, duplication
    Derived form: verb back up4
  5. backing, backup, championship, patronage - the act of providing approval and support; "his vigorous backing of the conservatives got him in trouble with progressives"
    --5 is a kind of blessing, approval, approving
    Derived form: verb back up1
,Verb back up has 5 senses
  1. support, back up - give moral or psychological support, aid, or courage to; "She supported him during the illness"; "Her children always backed her up"
    Derived form: noun backup5
    Sample sentence:
    Sam cannot back up Sue
  2. back up, back off, back down - move backwards from a certain position; "The bully had to back down"
    --2 is one way to withdraw, retreat, pull away, draw back, recede, pull back, retire, move back
    Sample sentences:
    Something ----s
    Somebody ----s
  3. back, back up - establish as valid or genuine; "Can you back up your claims?"
    --3 is one way to confirm, corroborate, sustain, substantiate, support, affirm
    Sample sentences:
    Somebody ----s something
    Something ----s something
  4. back up - make a copy of (a computer file) especially for storage in another place as a security cop; "You'd better back up these files!"
    --4 is one way to
    copy, re-create
    Derived form: noun backup4
    Sample sentence:
    Somebody ----s something
  5. clog, choke off, clog up, back up, congest, choke, foul - become or cause to become obstructed; "The leaves clog our drains in the Fall"; "The water pipe is backed up"
    --5 is one way to obstruct, obturate, impede, occlude, jam, block, close up
    Derived form: noun backup1
    Sample sentences:
    Something ----s
    Somebody ----s something
    Something ----s something