What does weekly-ordered transaction mean?

Is your confusion because you are mis-reading this as "weekly", meaning every 7 days, or was this a typo and you didn't understand what "weakly-ordered" means ?

Weakly-ordered would imply a transaction for which the completion through to final destination isn't too important to the transaction initiator, as opposed to a "strongly-ordered" transaction where the order this transaction completes in relation to other transactions is extremely important to the initiator.

An example of strongly ordered transactions would be ones configuring a peripheral, where you want to configure A, then  B, then C, and only move on to each configuration step when the previous one has completed.

Do you have some context for your question, where you saw this described ?