Between. For example, accompanied by four crescents, would mean between four crescents.
When a charge or ordinary is surrounded or placed between a number of other charges, it is said to be accompanied by those charges.
In the case of ordinaries there may be “natural” places for the accompanying charges to go, if the charges are to be placed in those “natural” positions, the position need not be mentioned in the blazon. For example, if a chevron is accompanied by two charges above and one charge below, that arrangement is deemed to be “natural” so the specific position of the charges might not be blazoned. When making your own blazons, it is always better to error on the side of too much information instead of crafting a blazon which might not properly describe your arms.