歃血为盟: smear the blood as a sign of the oath -- an old chinese practice; lick blood and swear; pledge each other in wine in which blood has been mixed; smear one's lips with its blood in token of
Example Sentences:
1.
Improbable friends pledged to be blood brothers . 萍水相逢的朋友歃血结成生死与共的兄弟。