[Maxima] nouns, verbs, why?

[Richard Hennessy]

Can you use this distinction between nouns and verbs to cause a function to have a name and definition but prevent it from ever 
being evaluated unless a specific command to evaluate it is issued?  I am thinking about pwdelta(x), I want it to never be evaluated 
even if x is known (except when I tell Maxima to evaluate it).

pwdelta(x):= if x=0 then inf else 0;

Rich