How to use table inside a newenvironment [duplicate]

I'm using a table inside a new environment to create a list of definitions, but some of the things being defined are two words. I want to have the first word on one line and the other word on the next line but everything I try gives an error or an incorrect out. (This works fine if it's only one word.) Here is what I have so far:

\documentclass{article}
\usepackage{fullpage}
\setlength\parindent{0pt}

\newenvironment{defn}[2]
{\begin{tabular}{p{1in} p{5in}}
\hfill\underline{#1} & #2
}
{\\ \end{tabular}}

\begin{document}

\begin{defn}
{Jib\\ Jab} {Here is the definition of the word Jib Jab}
\end{example}

\begin{defn}
{Def2} {Here is the definition of the word Def2}
\end{defn}

\end{document}


marked as duplicate by Martin Schröder, user13907, user36296, Werner tables StackExchange.ready(function() { if (StackExchange.options.isMobile) return; $('.dupe-hammer-message-hover:not(.hover-bound)').each(function() { var$hover = $(this).addClass('hover-bound'),$msg = $hover.siblings('.dupe-hammer-message');$hover.hover( function() { $hover.showInfoMessage('', { messageElement:$msg.clone().show(), transient: false, position: { my: 'bottom left', at: 'top center', offsetTop: -7 }, dismissable: false, relativeToBody: true }); }, function() { StackExchange.helpers.removeMessages(); } ); }); }); Nov 5 '16 at 5:18

• Your problem is \underline{Jib\\ Jab} which is not allowed us for underlining words. Welcome to site! – Zarko Nov 4 '16 at 23:30
• Welcome to TeX.SX! You can have a look at our starter guide to familiarize yourself further with our format. – Martin Schröder Nov 4 '16 at 23:35

Do you like to obtain something like this?

Command \underline{...} doesn't allow to break the underlined text. This can be done for example with use of package soul:

\documentclass{article}
\usepackage{array}
\usepackage{soul}
\setlength\parindent{0pt}

\newenvironment{defn}[2]
{\begin{tabular}{>{\raggedleft}p{1in} p{5in}}
\hfill\ul{#1} & #2
}
{\end{tabular}}

\begin{document}

\begin{defn}
{Jib\\ Jab}{Here is the definition of the word Jib Jab}
\end{defn}

\begin{defn}
{Def2} {Here is the definition of the word Def2}
\end{defn}

\end{document}