(Latin: æquus, equal; vocare, to call)
The use of a word, or phrase, having more than one meaning, with a view to concealing from one's questioner information which he has no right to seek, or to give which might unjustly embarrass or compromise the one interrogated.
This is wrong when the information is due by any obligation of justice or charity, but permissible and even advisable when the interrogation is impertinent or unjust; it is practised universally in such cases even by those who affect to deem it wrong.
Excuses for not admitting visitors when inconvenient and evasive and misleading answers of professional men who are obliged to protect secrets, are examples of justifiable equivocation.
A classic instance and discussion of this subject is given by Newman in Note C in the appendix to his "Apologia," that of Saint Athanasius when asked by his pursuing persecutors, "Have you seen Athanasius 1" "Yes," he replied, "he is close to you," and they, misled, continued on their course.
New Catholic Dictionary