It's both. A file format need not be compressed to be lossless.
Well, lossless is an audio format that uses an algorithm to compress audio data...without loss, etc.
Chewy seems to be playing semantics.
Lossless merely implies that all of the information from the original file is available in the new file. AIFF is lossless.
From Wiki:
"Standard AIFF is a leading format (along with SDII and WAV) used by professional-level audio and video applications, and unlike the better-known lossy MP3 format, it is non-compressed (which aids rapid streaming of multiple audio files from disk to the application), and lossless. Like any non-compressed, lossless format, it uses much more disk space than MP3—about 10MB for one minute of stereo audio at a sample rate of 44.1 kHz and a sample size of 16 bits."