Both .x3d and .lwo files are used to store 3D models and thus can most likely be converted from one to another. One of the known programs that can import .x3d and export .lwo files is for example Blender, but it is likely you can find more suitable for this type of conversion.
Convert X3D graphics model to LightWave object file.
We have found 2 software records in our database eligible for .x3d to .lwo file format conversion.
Microsoft Windows software - convert x3d to lwo on Windows
A very popular free program used for work with 3D graphics
Convert from x3d file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned x3d to lwo. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
A 3D CAD translation softwate