Mostly; ordinarily; usually — indicates what typically happens or is the normal case.
たいていの学生は朝の授業に出席する。
Most students attend the morning classes.
たいていは予約が必要だが、今日は空いているかもしれない。
Usually you need a reservation, but today it might be open.
彼の話はたいてい面白い。
His stories are usually interesting.
Probably — expresses a speaker's conjecture that something is likely.
彼はたいてい遅刻するから、今日も遅れるだろう。
He usually arrives late, so he'll probably be late today too.
たいていの人はその説明で納得するだろう。
Most people will probably be satisfied with that explanation.
Most; almost all — as a noun phrase referring to the majority.
大抵の人は朝食を食べる。
Most people eat breakfast.
その本は大抵の書店で手に入る。
That book is available at most bookstores.
Used before a negation to mean 'usually not' — indicating that something normally does not occur.
大抵はそんなに困らないが、今回は違う。
Usually it's not that troublesome, but this time it's different.
彼は大抵怒らないが、今日は珍しく怒った。
He usually doesn't get angry, but he was unusually angry today.
Proper; appropriate; moderate — often used in expressions like 'make it moderate' (e.g., stop or moderate something).
飲み会は大抵にしておきなさい。
Don't overdo it at the drinking party — keep it moderate.
その冗談は大抵にしなさい。みんな不快に思っているよ。
Enough with that joke. Everyone is uncomfortable.