Linehaul generally means to the transport of freight by road between cities and usually a distance greater than 100Km. So, a linehaul delay would be a hold up in the trucking link of the delivery chain, say a breakdown, strike, bad weather or something else.
Hope this helps, Jackson.
If it’s coming from outside Canada it could be delayed by customs, I’m not sure why else there would be a delay unless there’s bad weather or something stopping the carrier from getting it to you. Edit: seems odd that it’s being held by the carrier, could be that whoever the driver is that does your area was off and they couldn’t get cover for that day. If it’s still delayed tomorrow I would call (if possible) to find out what’s happening with it.