[CWOT] "Complete waste of time"

[CYA] "See you"; used as a goodbye (see "[cu]").

[cyberbug] someone who spends too much time on the Internet

[C|N\> K] "coffee through nose into keyboard"; a Unix-ism meaning, involving […]

[D2] "Diablo_II"

[dab] See: [SMACK-DAB] or [SMACK-TO DAB].

[dagger] See: [CLOAK-AND-DAGGER], [LOOK DAGGERS].

[daily dozen] {n.}, {informal} Gymnastic exercises; especially, several different exercises done […]

[daisy] See: [PUSH UP DAISIES].

[dam] See: [WATER OVER THE DAM].