Two words
May be 2 words combined (cap+serius) If not obvious, probably incorrect
seri.us ADJ 1 1 NOM S N COMP
seri.us ADJ 1 1 VOC S N COMP
seri.us ADJ 1 1 ACC S N COMP
serus, sera -um, serior -or -us, serissimus -a -um ADJ [XXXBX]
late; too late; slow, tardy; after the expected/proper time; at a late hour;
seri.us ADJ 1 1 NOM S M POS
serius, seria, serium ADJ [XXXDX] lesser
serious, grave;
serius ADV POS
serius ADV [XXXDX] lesser
later, too late;
serius ADV COMP
sero, serius, serissime ADV [XXXBO]
late, at a late hour, tardily; of a late period; too late (COMP);
*

Credits:
This, our local install of the popular standby Whitaker's Words, is possible thanks to the resurrection of the venerable project at William Whitaker's Words, where you will also find extensive documentation. The corresponding GitHub repository is where you can submit issues about missing forms and analyses.
This web interface by Walter M. Shandruk.