butt in (phrasal verb of butt)
take part in a conversation or activity, or enter somewhere, without being invited or expected.
"sorry to butt in on you"
(all) by one's lonesome idiom
Save Word
Definition of (all) by one's lonesome
informal
: without anyone else : entirely alone
Ex) He sat by his lonesome at the dinner table.
She made the cake all by her lonesome.