acyl(n = noun.substance) acyl group - any group or radical of the form RCO- where R is an organic group; "an example of the acyl group is the acetyl group"
An acid radical, as acetyl, malonyl, or benzoyl. An acyl radical can be depicted as R-CO-, where -CO- is the carbonyl group, and R is the group that characterizes the acyl moiety. [Webster 1913 Suppl.]