In jazz, a repeated melodic phrase as a background accompaniment for a soloist. Probably from the word refrain.

The basis of rock music. A repeated melodic/rhythmic phrase played in a particular manner, as in jazz and blues. In rock music, it is typically executed on a 6-string guitar.
These songs are noted for their riffs:
Sabbath Bloody Sabbath
Highway to Hell
Enter Sandman
(I can't get no) Satisfaction

Resource Interface File Format.

The file format informally known as .wav and .avi. This is Microsoft's audio/video format, innovatively very similar in structure with Apple's AIFF format.

Technically, it's a rather simple format, one of the most basic binary file structures. It's based on chunks that have

1. a 4-byte type identifier (known as a fourcc),
2. 4-byte length field that tells how many bytes the data field has, and
3. the data field itself.

The data fields can contain other RIFF chunks.

Here's an easy algorithm for ripping a .wav to raw data (assuming the file is PCM and the thing didn't add too much extra baggage to the file): Skip leading bytes until you find character sequence "data", read next four bytes and interpret as the size, then read that many bytes.

In the online comic strip Sluggy Freelance, Riff is a freelance bum/mad scientistish inventor with a reputation for blowing things up. He is (was) the best friend of the star of the strip. He almost always seems to have an excessively powerful weapon handy, and is always (so far as I can recall) seen in his trenchcoat and sunglasses. Son of Dr. Lorna, the radio talkshow host. Has a pet ferret, Kiki. Gwynn used to be his girlfriend, but they are currently broken up. Currently, Riff is going up against HeretiCorp, the evil company he had been freelancing for, because they kidnapped Aylee after he mentioned her in a report, and they've kidnapped his friends to get information from them. Is there anything I missed? Let me check my notes.