Testicles, or used as an exclamation meaning nonsense or rubbish; variant spelling of 'bollocks.'
From Old English 'beallucas' (testicles) with '-ocks' pluralization. The 'a' spelling is a dialectal variant, particularly in American English.
British and American English took the same medieval word and spelled it differently—'bollocks' vs 'ballocks' shows how English split into regional dialects centuries ago.
Complete word intelligence in one call. Free tier — 50 lookups/day.