SharePoint 2013 :Adding shared properties to a term set using PowerShell

To update or create a shared property for a term in your term store run the following script.

#Load SharePoint PowerShell Snap In
Add-PSSnapin Microsoft.SharePoint.PowerShell;

#Get Taxonomy Session
$session =  new-object Microsoft.SharePoint.Taxonomy.TaxonomySession(Central Admin URL);
#Get Managed Metadata Service
$Store = $Session.TermStores[“Managed Metadata Service”];
#Get Term Group
$Group = $Store.Groups[“Group Name”];
#Get Term Set
$TermSet = $Group.TermSets[“Term Set Name”];
#Get Term
$Term = $TermSet.Terms[“Term Name”];
#Add Property, if property exists it will be over written
$Term.SetCustomProperty(“Property Name”, “Property Value”);
#Commit Changes
$Store.CommitAll();