about 80%; mostly; almost certainly
Used to indicate that something is roughly 80% complete, or that a situation is largely settled. The 'almost certainly' sense is a figurative extension of the quantitative meaning.
The construction is about 80% finished.
It's almost certain that he will come.
大体 is a general 'mostly' or 'roughly', whereas 八割方 gives a more precise estimate of around 80%.
Standard kanji spelling.
Variant using Arabic numeral 8; common in casual or digital writing.
Compound of 八割 (80%) + 方 (direction, side, approximately). The 方 here functions as a suffix meaning 'about' or 'in the range of'.