Pickle deserialization refers to the process of reconstructing Python objects from a byte stream using the pickle module. While pickle is convenient for saving and loading Python objects, it can be dangerous when used with untrusted data. Maliciously crafted pickle data can execute arbitrary code during deserialization, leading to severe security vulnerabilities such as remote code execution. Therefore, it is strongly advised to avoid unpickling data received from untrusted or unauthenticated sources. Safer serialization formats, like JSON, are recommended when exchanging data between systems or users.