afterbeat
/ˈɑːftəbiːt/ /ˈaftəbiːt/noun
1 Medicine. A beat of the heart or of the pulse following a main or normal beat; (in later use) specifically an extrasystole. Now rare.
2An ending to a trill comprising two notes, the first being one step lower than the main note, the second being the main note itself.
3An offbeat; an accentuated backbeat.
Origin
Mid 19th century. From after- + beat. In sense 1 after German Nachschlag.