Source : Webster's Revised Unabridged Dictionary (1913)

Understand \Un`der*stand"\ ([u^]n`d[~e]r*st[a^]nd"), v. t. [imp.
   & p. p. {Understood}, and Archaic {Understanded}; p. pr. &
   vb. n. {Understanding}.] [OE. understanden, AS. understandan,
   literally, to stand under; cf. AS. forstandan to understand,
   G. verstehen. The development of sense is not clear. See
   {Under}, and {Stand}.]
   1. To have just and adequate ideas of; to apprehended the
      meaning or intention of; to have knowledge of; to
      comprehend; to know; as, to understand a problem in
      Euclid; to understand a proposition or a declaration; the
      court understands the advocate or his argument; to
      understand the sacred oracles; to understand a nod or a
      wink.

Understood \Un`der*stood"\,
   imp. & p. p. of {Understand}.

Source : WordNet®

understood
     See {understand}

understand
     v 1: know and comprehend the nature or meaning of; "She did not
          understand her husband"; "I understand what she means"
     2: perceive (an idea or situation) mentally; "Now I see!"; "I
        just can't see your point"; "Does she realize how
        important this decision is?"; "I don't understand the
        idea" [syn: {realize}, {realise}, {see}]
     3: make sense of a language; "She understands French"; "Can you
        read Greek?" [syn: {read}, {interpret}, {translate}]
     4: believe to be the case; "I understand you have no previous
        experience?" [syn: {infer}]
     5: be understanding of; "You don't need to explain--I
        understand!" [syn: {sympathize}, {sympathise}, {empathize},
         {empathise}]
     [also: {understood}]

understood
     adj 1: fully apprehended as to purport or meaning or explanation;
            "the understood conditions of troop withdrawal were
            clear" [ant: {ununderstood}]
     2: indicated by necessary connotation though not expressed
        directly; "gave silent consent"; "a tacit agreement"; "the
        understood provisos of a custody agreement" [syn: {implied},
         {silent}, {tacit}]