Definition of yacking:
(n) :
(England, dialectal, possibly obsolete) An oak.
(n) :
(UK, thieves slang, obsolete) A watch (timepiece).
(v) :
Alternative form of yak (“talk; vomit”). [(slang, intransitive) To talk, particularly informally but persistently; to chatter or prattle.]
(n) :
Alternative form of yak (“chatter; talk”). [An ox-like mammal native to the Himalayas, Mongolia, Myanmar, and Tibet with dark, long, and silky hair, a horse-like tail, and a full, bushy mane.]