定例ミーティングって英語でなんて言うの？

'Bi' (2) or Tri (3) may be placed before 'meeting' to indicate twice or three times. Eg We have trimonthly meetings at the moment. = three meetings a month.

"annual meeting' means its conducted/held once every year.
"weekly meeting" means it is conduced once every week.
"monthly meeting" means its conducted once every month.

It is quite usual for a company's board of directors to have a regular or "recurring meeting" or a specific fixed appointment...every week / month / quarter / etc ...to discuss policy and any developments within the company.
"We are so busy right now we have changed our recurring meeting...to once a month"

biweekly - this can either mean:
1/ once every 2 weeks -or-
2/ twice in a week

bimonthly - this can either mean:
1/ once every 2 months -or-
2/ twice in a month

Biweekly/bimonthly is very ambiguous, so be sure to explain what you mean by this.

A weekly meeting is held once a week on any chosen day of the week.
A fortnightly meeting is held once every two weeks.
A monthly meeting is held once every month.

1. These meeting are held regularly.
   これらの会議は定期的に開催されます。
   Some companies have meetings that they hold on a regular basis, sometimes these meetings are held every week, every month, every quarter etc.

   2. Weekly meetings.
      毎週のミーティング
      Weekly meetings means meetings that are held once every week.