verb in custom command

As already mentioned in comment, verbatim or its short form verb is a different beast altogether. If you must pass verbatim stuff as arguments, you could consider a fancyvrb work-around.

Using fancyvrb you can save and restore your verbatim commands in the following way:

usepackage{fancyvrb}% http://ctan.org/pkg/fancyvrb
DefineShortVerb{#}% # denotes verbatim opening/closing character
SaveVerb{VerbA}#(echo 5+4 | bc)#
SaveVerb{VerbB}#$((5+4))#

This stores (echo 5+4 | bc) as-is in VerbA, and $((5+4)) in VerbB, which can be used (restored) later by means of UseVerb{VerbA} and UseVerb{VerbB} respectively. Here is a minimal working example:

documentclass{article}
usepackage{fancyvrb}
newcommanddd[2]{item[texttt{#1}] #2}
begin{document}
DefineShortVerb{#}% # denotes verbatim opening/closing character
SaveVerb{VerbA}#(echo 5+4 | bc)#
SaveVerb{VerbB}#$((5+4))#
begin{description}
  dd{bc}{text UseVerb{VerbA} text UseVerb{VerbB} text}
end{description}
end{document}

---

Edit: A similar work-around exist using the verbdef package. It provides verbdef{<cmd>}{<verb>} that defines <cmd> with verbatim <verb> content. The following MWE produces the same output as above:

documentclass{article}
usepackage{verbdef}
newcommanddd[2]{item[texttt{#1}] #2}
begin{document}
verbdefVerbA{(echo 5+4 | bc)}
verbdefVerbB{$((5+4))}
begin{description}
  dd{bc}{text VerbA text VerbB text}
end{description}
end{document}

Use the following:

newcommanddd[2]{texttt{detokenize{#1}} #2}

This will print #1 vermbatim.

Nowadays you can use the more "robust" Verb from fvextra package.

Note both Verb|...| and Verb{...} is supported (with some restrictions). Also when used as argument, don't use # as delimiters.

documentclass{article}
usepackage{fvextra}
newcommanddd[2]{item[texttt{#1}] #2}

begin{document}
begin{description}
  dd{bc}{text Verb{$(echo 5+4 | bc)} text Verb{$((5+4))} text}
end{description}
end{document}