Get a list of synonyms for a given term. This is heavily based on code from a question here: https://stackoverflow.com/q/49899308/361842

Thesaurus.cs

void Main()
{
	using (var thesaurus = new Thesaurus())
	{
		foreach (var term in (new string[]{"dictionary","hot","actor","code"}))
		{
			Debug.WriteLine(term);
			foreach (var value in thesaurus.GetSynonyms(term))
			{
				Debug.WriteLine($"- {value}");
			}
		}
	}
}

public class Thesaurus: IDisposable
{

	private Microsoft.Office.Interop.Word.Application appWord;
	private object objLanguage;

	public Thesaurus()
	{
		appWord = new Microsoft.Office.Interop.Word.Application();
		objLanguage = Microsoft.Office.Interop.Word.WdLanguageID.wdEnglishUS;
	}

	public IEnumerable<string> GetSynonyms(string term)
	{
		var si = appWord.get_SynonymInfo(term, ref (objLanguage)); //Microsoft.Office.Interop.Word.SynonymInfo
		foreach (var meaning in (si.MeaningList as Array))
		{
			yield return meaning.ToString();
		}
		System.Runtime.InteropServices.Marshal.ReleaseComObject(si);
		si = null;
	}
	
	public void Dispose() 
	{  
		Dispose(true);  
		GC.SuppressFinalize(this);  
	}  

	protected virtual void Dispose(bool disposing) 
	{  
		objLanguage = null;
		if (disposing)
		{  
			if (appWord != null) 
			{
				appWord.Quit(); //if this isn't called, you'll see winword.exe hanging around in your processes
				System.Runtime.InteropServices.Marshal.ReleaseComObject(appWord);  
			}
			GC.Collect();
			GC.WaitForPendingFinalizers();
		}  
		appWord = null;
	}  
}

Output of above example:

dictionary
- lexicon
hot
- warm
- sweltering
- spicy
- passionate
actor
- performer
code
- cypher
- program
- system
- cypher