That would be :bd. :help :bd in vim 8.2 gives:
:[N]bd[elete][!] *:bd* *:bdel* *:bdelete* *E516*:bd[elete][!] [N] Unload buffer [N] (default: current buffer) and delete it from the buffer list. If the buffer was changed, this fails, unless when [!] is specified, in which case changes are lost. The file remains unaffected. Any windows for this buffer are closed. If buffer [N] is the current buffer, another buffer will be displayed instead. This is the most recent entry in the jump list that points into a loaded buffer. Actually, the buffer isn't completely deleted, it is removed from the buffer list |unlisted-buffer| and option values, variables and mappings/abbreviations for the buffer are cleared. Examples: :.,$-bdelete " delete buffers from the current one to" last but one :%bdelete " delete all buffers
