Hello katlaughing!
Domo originally means "very", "somewhat", or, if used in the negative meaning, "by any means".
e.g. Domo arigato.--Thank you very much.
Sore wa (It) domo(somewhat) hen(strange) da(is).--It is somewhat strange.
Kare wa (He) domo(by any means) 80 sai(years old) niwa(-) mie(look) nai(not).--He does not look 80 years old by any means.
Young people (and some older ones) sometimes use "domo" for "domo arigato", but they are not polite.
Bonan sanon!