Do you lithp?

Random House Webster´s Dictionary defines "to lisp" as: "a speech defect consisting in pronouncing s and z like or nearly like the th-sounds of thin and this, respectively." Lisp would sound as "lithp," missing as "mithing," pass as "path," zoo as "thoo." Although common, this is considered a speech defect.
In Spanish this is called "ceceo", and M. Moliner defines "cecear" as "Pronunciar las eses como ces, como peculiaridad lingüística de ciertas regiones o por defecto de pronunciación." Sopa would be pronounced as "zopa", or in English "thopa."
In the so-called Castilian Spanish this is easy to detect, but not so in those who do not pronounce the "z" similar to the English "th." But still the speech defect is there and can be detected.  "Casar" y "cazar" are pronounced the same by the lisper.

In French it is "zézayer."
In Galego it is "cecear."
In German, "lispeln."
In Italian, "blesità."
In Catalan a lispers is a "xafallos."
Lisping is caused by a wrong position of the tongue in the mouth which in time becomes a habit and a way of speaking.